What Gears Sets Are Available?
See Technical – Gears for a table listing available gear sets, R&P, speed at redline and RPM at upshift.
Japanese "Short" Gears
[HS] I propose we upgrade the nomenclature on the "shorties" or "short gears." I’m going to start referring to the five speed with Japanese gears as the "Japanese five speed," and to the same transaxle with the 4.55 ring and pinion as the "4.55 Japanese five speed"… those Japanese-geared five speeds with the 4.235 ring and pinion can simply be referred to as an "R transaxle."
[BJ] I agree with HS and would prefer adoption the “Japanese five speed” or “JDM 5spd” nomenclature to replace the somewhat incorrect “short gears”.
[HS] All Japanese (not European or anywhere else as far as I know) NSX come with the different (shorter) 2nd, 3rd and 4th gears — their ring and pinion is the same as ours (4.062). The NSX-R comes with the same, Japanese, gearset, but with a slightly lower R&P (4.235).
For Europe our (taller) gearset makes sense for their ultra-fast freeway driving, but not for their twisty back roads.
[JPA] It was interesting to notice the comments from our recent travelers to Japan about someone who asked the Japanese why there were two sets of gears, one for America and one for Japan. The response from the spokesperson was there’s a difference in driving conditions. I guess that means in the USA there are more open highways, therefore the higher gears. IMO, no matter what, whether on city streets or the open highway, the short gears/R&P are a big, positive improvement.
[BJB] As you can see, most of the improvement is made in the shift to second.
|Shift||Stock ’91-’94||Short Gears (4.06 R&P)|
|1-2||4433 RPM||5013 RPM|
|2-3||5698 RPM||5705 RPM|
|3-4||6262 RPM||5824 RPM|
|4-5||6284 RPM||5983 RPM|
[KS] The point of close-ratio gears is to keep the engine at the highest possible RPM and therefore HP. The stock gears are not optimal because there’s a gap between 1 and 2 that makes the revs drop from 8000 to 4499, which is lower in power than the "short" gears, which make revs drop from 8000 to 5085. So far, so good (and this is why there’s greater acceleration in that 40-60 mph band with the short gears).
However, once you get into the power band in second gear, the gear ratios on your upshifts from that point on actually keep your revs HIGHER with the stock gears than with the short gears (except the second-third shift, which is almost identical). More specifically, when you upshift from redline, here’s where your revs are in the next higher gear:
second-third places revs at 5698 stock gears, at 5738 short gearsthird-fourth places revs at 6289 stock gears, at 5903 short gearsfourth-fifth places revs at 6378 stock gears, at 5971 short gears
So therefore the gears from third to fifth are actually closer-ratio gears in the stock setup than in the short gear setup. Therefore your acceleration (assuming higher revs means higher horsepower) past 60 mph or so should actually be FASTER with the stock gears than the short gears, because they achieve the same objective with those upper gears as the short gears do with the lower gears – keeping the revs up.
(Above numbers assume a comparison between stock ’91-93 gears vs short gears with stock R&P.)
[LL] If you don’t care about second gear acceleration, don’t get the gears. The short gears are primarily for street pleasure. IMO second gear acceleration on the street is of *primary* import, thats where I get much of my gollies. How many zillions of times on the street do you brake and downshift into second for a slow 20-30 mph corner and them power out of it. The stock NSX is a dog here, the short second should really help here.
[LL] The calculated rpm’s after shifting from 1rst to 2nd are 4506 for the standard tranny gears and 5084 for the short second gear. These are not the numbers you see on the tach because of clutch slipage and tach lag time. Tach’s are generally not very accurate BTW, *maybe* ours is. But the above numbers are a reasonably accurate method of determining power differences. One can add say 600 rpm to the before and after numbers to further accurize the results.
There is approx 29 more HP available at the higher short gear numbers that effects acceleration. Thats why we want-em, plain and simple. This is about a 14% increase in power at this point.
The numbers from 2-3 are 5687/5740, 3-4 6310/5903 and 4-5 6358/5972. As you can see the numbers backfire going into 4th and 5th. This of course doesn’t come into play until 115 mph, so is a fair trade for most of us. This is where the 6-spd shines, it keeps the r’s up at high speeds. I believe all these numbers are on somones web site. I have all the numbers on all possible combinations of trannys and R&P’s, but it’s not in a transmitable database at this time. I can scan it though.
The US prices for the short gears (less shims, gaskets, etc), assuming you replace 1st, 2nd, 3rd and 4th: $964.11 plus tax. The mainshaft alone is $400.
The NSXs sold in Japan (both regular *and* NSX-R) use different gear ratios (for 2nd, 3rd and 4th gears only) than those sold elsewhere in the world. The NSX-R also uses a different ring and pinion (4.235, all others use 4.062). Acura in the US *will* order the Japanese gearsets. They will take awhile to get here (and be twice the price of the same parts in Japan, such is life). Just order the part numbers through any dealer.
Parts List For "Short Gears"
23210-PR8-020, main shaft (contains 1st and 2nd gear) (22,200 Yen)
23441-PR8-020, 3rd gear for mainshaft (6,100 Yen)
23451-PR8-010, 4th gear for mainshaft (6,100 Yen)
23581-PR8-020, 5th gear for mainshaft (6,100 Yen)
23421-PR8-020, 1st gear (3.071) for countershaft (7,300 Yen)
23431-PR8-010, 2nd gear (1.952) for countershaft (6,600 Yen)
23471-PR8-000, 3rd gear (1.400) for countershaft (5,000 Yen)
23481-PR8-000, 4th gear (1.033) for countershaft ( 5,000 Yen)
23461-PR8-000, 5th gear (0.771) for countershaft (3,900 Yen)
The "short gears" are the ideal gear ratio set for running track events or twisty back roads, but it leaves the stock 5th gear intact for highway cruising. There *will* however, be a large space between 4th and 5th gears. You might consider adding the Comptech 4.55 ring and pinion (it shouldn’t limit the NSX top speed since you can’t pull 8,000 rpm in 5th now, but should be able to with the lower R&P).
1st and 5th gears are the same in *all* NSX cars, so if your transmission doesn’t have too many miles on it, you can consider re-using your existing 5th gear.
Since 1st and 2nd gears are part of the mainshaft, you should order a new countershaft first, even though you already have this gear in your transmission. It’s been my experience that you should replace both sets of gears for a given ratio (wear patterns, noise). You may also want to replace the gear bearings, the case bearings will probably be OK unless your car has a lot of miles. I’m going to do it.
Japanese 5-speed gear sets ("short gears") are available from RM Racing and Dali Racing. RM’s price is $799 a set or $1,600 installed.
[RC] The short gears are the best money I’ve ever spent on an upgrade to any car (followed closely by Randy’s brakes and the B&B exhaust)!!
Problem with notchy shifting on early ’91 cars with short gears
[BMC – 99/03/13] I spoke to the guys at Comptech and they warned me to be very careful to tell my mechanic to pay
attention to the shim width in conjunction with the gears on the mainshaft. Apparently the width of the 2nd gear on the short gear mainshaft is different from the one in the cars in this range (I guess they went with a different supplier after the problem was discovered). The result is that if the shims are not sized properly, the tranny case is difficult to get closed and shifting can be notchy...
This issue concerns mainshafts originally installed on early ’91’s in gear boxes w/transmission numbers through #1000768. The width of 2nd gear on these shafts were cut too narrow. Rather than throw them all out, Honda decided to add an extra shim between 2nd and 3rd in order to bump 3rd out the correct amount to line up with the corresponding gear on the countershaft.
When installing the short gear mainshaft, however, 2nd is the correct width (the problem was corrected after those transmission numbers). Therefore, the extra shim MUST NOT be installed to insure proper alignment. Installing it results in notchiness.
Comptech 5-Speed to 6-Speed Conversion
1991-1996 manual transmission cars use a 5-speed. Starting with the 1997 model year, the factory upgraded to a 6-speed for the manual transmissions. The 6-speed uses the same (4.062) R&P as the 5-speed — and:
1st gear is the same as all NSX 1st gears
2nd gear is about the same as the "short" second gear
3rd gear is about the same as the "short" third gear
4th gear is *shorter* than the "short" fourth gear
5th gear is almost the same as the *stock* fourth gear
6th gear is a tick *taller* than the 5-speed's fifth gear
Unlike the 5-speed, all countries use the same 6-speed ratios.
[MBA – 2000/1/22] The six speed goes right in place of the five speed, but does not work with the double disc clutch. When you replace the 5 speed with a 6 speed, you must install either the factory ’97+ single disc clutch, which requires a new flywheel… OR (my choice) the Comptech single disc PowerGrip clutch. There is no way to install it on a double disc clutch, or to install Acura’s single disc clutch on the flywheel made for the double.
[LE] Comptech offers a 5-speed to 6-speed conversion package. It includes factory 6-speed gearbox modified by Comptech, electronics for the reverse lockout, and their Comptech PowerGrip Clutch Package with Lightweight Aluminum Flywheel (not a lightened factory flywheel). Price: $6,895. The PowerGrip Clutch Package is normally $1,850 by itself so you’re really only paying $5,045 for the rest of the kit, which makes it pretty attractive vs. short gears and a R&P I think.
The redline speeds for each gear with various gear sets is at follows (in MPH):
Stock US (5-speed): 45, 81, 114, 144, 186 (theoretical – top speed is of course drag-limited below 186)
Japanese "short" gears (5-speed): 40, 65, 90, 124, 166.
Stock US six speed: 46, 72, 99, 126, 155, 168
[KS] As you can see, the 6-speed has better gearing (than the "short" gears) for 1st-5th, with a too-tall 6th gear. Do the 4.55 Comptech ring and pinion to a 6-speed, and you’d have a super-duper tranny for the US.
The six speed ratios for second and third gears are similar to those of the Japanese "short" gears. However, the ratios for fourth through sixth allow you to stay closer to the power peak, and they are nicely spaced, by interleaving the ratios for fourth and fifth in the stock five-speed. So the six-speed remedies the shortcomings (pun intended) of the Japanese gears once you get above third gear (which redlines around 100 mph).
Bottom line, then, is that once you get above 100 mph, the six speed will have a significant advantage in acceleration over the five speed with the Japanese gears. Even the stock five-speed will have an advantage above 100 mph over the Japanese gears. But the six-speed also gives the advantage of better acceleration in the 40-60 mph band following the one-two upshift. The best of both worlds, if you will.
[STH – 99/2/21] Several of you has asked me privately for details on the 6-spd conversion for 1996 and earlier 5-spd transmissions, so I am posting this summary. I initially did the Japanese short gears and the Comptech 4.55 R&P at the same time. In retrospect, this was a big mistake because I didn’t get a chance to try out the "shorties" alone. The two combined, in my opinion, is too much. This is strictly a matter of preference since the person whom I sold my transmission to seems quite happy with the setup. I did not like the gear whine nor did I like running very high RPMs at highway cruising speeds. From what I understand, the gear whine was most prominent on the earlier Comptech 4.55 R&P versions and Comptech is replacing the one in my old transmission (free of charge?).
Now, for the 6-spd… parts needed & list pricing:
|Part Number||Description||Quantity||Price (each)|
|A 20011-PR8-660||OEM Honda 6-spd transmission||1||$5259.12|
| OEM Transmission Fluid
-or- Redline MT90
|From Comptech||6th Gear Lock-out kit / adaptor||1||$664.00|
|From Comptech||PowerGrip Clutch||1||$2100.00|
These are list prices, but I got a pretty good deal from Davis Acura because I think I spent enough money there to put Glenn’s new daughter through her first year of college. 😉 YMMV, call them and see what they can do for you.
Transmission: a very nice close ratio gearbox. It feels awesome… and I love the 6th gear on the highway. I no longer need to turn up the radio on long drives, since the interior noise has diminished appreciably. The 1-2 shift is almost like the 5-spd with the shorties and R&P, although not as brutal. If anyone has driven the 5-spd w/ shorties and the 4.55 R&P, you know that you can easily break the rear tires lose on the 1-2 shift. You can snicker through the gears 1-5 easily… and you still have the overdrive 6th if you just want to cruise.
PowerGrip Clutch w/ Al flywheel: Since Comptech gave a huge disclaimer that if I beat on the clutch from the beginning, it would chatter and lead to premature wear, I absolutely babied this clutch for the first 500 miles. Now, after 1000 miles on the clutch, it still chatters slightly. The pedal pressure required is significantly more than stock. You should definitely drive an NSX equipped with one before buying. I drove Dave Davis’s car and it felt exactly like the Sachs HD clutch on my M3, so I was fine with it. Maybe if I get stuck in New York City traffic for a few hours, I won’t be as happy… I liked RM Racing’s clutch feel a lot better… I called up Randy just to verify that he did not have a clutch application available for the 6-spd before deciding on the Comptech one.
Well, that’s about it. If you can sell your current tranny like I did, it definitely eases the pain with the $$. One other thing I should mention is that tax was huge, as you can imagine (enough to cover labor!), with a purchase like this… so if you do it, you might also want to consider buying the transmission via mail order from a number of Acura dealers that do this.
What Ring & Pinion Sets Are Available?
Japanese NSX-R Ring & Pinion (for 5-speed)
[LL] Here are the numbers necessary for the installation of the R gear into a 91-94 model.
Final drive gear(Ring gear): 41233-PR8-J00
Oil pump gear: 21173-PR8-J00
If you also want to upgrade your differential to R specs(and I think we should,especially if you’ve added power), you will also want to get the following:
Differential collar: 41581-PR8-J00
Spring plate: 41696-PR8-000
This spring plate is a standard model NSX part, however the R uses two of them to increase the clutch pack pressure. The torque to put on this pack is not known at this time, we need to get the number from a service manual that
covers the R model, I'm going to work on this.
This clip was also recommended by Japan, I haven’t yet figured out what the hell it is. It’s only a few bucks though.
It’s my belief at this time that to put this gear set into a 95-96 will require changing to the early non-torque sensitive differential.
Cost for the above is around $690 plus $200 shipping. The only person able to get these parts so far is Ben Miller of CSI. He has all these numbers on file. Reach him at CSiLA@compuserve.com or 714-879-7955.
[MJ] Required Disclosures: My car is a ’92 with the "short" gears and OEM 94+ tires and wheels. (It also has lots of other mods but they do not count at the moment)
Short version: You get a 4.5% increase in the rev’s in each gear, or a 4.5% increase in the available torque. (in my case that is 9.0 ft/lbs) The car feels lighter and has more "zip" similar to the feeling you get when you go from OEM USA 5 spd. to the "shortie" (Japanese) 5 spd. gear set without the "buzzy" (high rev) engine feeling.
Long version: For those of you that have been sleeping through this whole ordeal, the NSX/R mod is a Honda factory 4.235 R&P (stock 4.06) that we were led to believe was not compatible with the ’91-’94 models as the "R" was a quasi
'95 model and most likely had the beveled (quieter) R&P and improved rear end design.
As it turns out, the parts we got were a 100% drop in kit. No additional parts were required for it to go, except some OEM (usa parts) replacement seals. (I was told by the dealer that you needed to replace them if you took everything apart so all the goo would not leak out, some of you pennie pinchers might get away without doing that – YMMV of course)
Larry sez in a previous post:
" …To backtrack a bit, the "differential preset torque" discussed above is from 43-101 ft lbs listed in the standard manual. This is one hell of a big range, It wouldn’t surprise me if the 101 number is for the R.."
Mine was measured @ 60 ft lbs. and the tech left it alone – "go try it" was the response I got to my request to turn it all the way up.
So, I LIKE IT – it is just like doing the shortie gears and hitting that 1-2 shift, it just "feels" lighter on it’s feet. I have only had one other NSX’r try it and they were :-)-ing.
Price is $950.00/set + shipping to you. (from Dali Racing)
[A/H] The beveled gears are for the "Torque Sensitive Diff". The bevel comes into play when you are on the gas: More torque pushing the clutch pack tigher. When you come off the gas it loosens up the clutch pack to make it easier to turn.
If you UP the break away torque it will make your car "push" in the corners because the rear tires will want to stay locked together.
[BM] Thought I would finally post this review to the list as I’ve enjoyed my first weekend of driving my ’92 after having the Snap Ring fix, Short Gears, Type R Ring & Pinion, and Comptech Rear Beam Bushings and Toe Links installed.
… Whoa, what a difference!!! …
ICBW, but I believe this is the second known install of the Type R R&P and there were some peculiarities surrounding the install as Mark Johnson and Larry Long are well familiar (having listened to the whole diatribe over the last 10 days). For the rest here is the summary:
Thanks to Larry’s extensive research, when we first ordered the parts we ordered every part that was listed in the R parts book for the differential and transmission that was different from the U.S. version (except the gears which we are all familiar with). They are listed below:
|Part Description||Part Number|
|Oil Pump Gear||21173-PR8-J00|
The need for the first three was obvious; the last two were less so. In addition, there was a question as to what preset torque to set the differential pack to once it was all bolted back together (the spec range is 43-101 lb-ft — quite a large range). Then at NSXpo, we were able to actually look at the R parts book once again and discovered on closer examination that one more part was required, not because it’s part number was different but because the R calls for two of them to the U.S. car’s one: (Spring Plate, part #41696-PR8-000)
Note that the first group of parts all end in J00, signifying Japanese-specific parts while the last does not.
To make a long story short, after just opening up the gearbox and taking our time, my mechanic and I were able to figure it all out. It turns out that the extra spring plate is added to the Type R differential to increase the preset torque in the differential pack, in order to decrease the likelihood of inside wheelspin (for example, when exiting a corner such as Turn 11 at Mid-Ohio). [Note: Later model NSX’s (’97+ ?) do not need this due to a new "torque-load" differential] The different Stopper Plate is necessary to provide extra room for the additional spring plate without increasing the stack height of the assembled clutch pack. Once these two parts were installed, the Preset Torque went from 52 to 105 lb-ft (as measured in the vise). For any that are interested, the specifics can be found on pages 15-3 and 15-4 in the ’92 Service Manual.
Finally, the Return Spring goes on the Shift Select mechanism and simply provides a stronger gear shift return to neutral from 5th/reverse. I don’t know why the Type R calls for this — perhaps it has something to do with the 6-speed. It is certainly stronger — I have found that occasionally coming out of 5th, I have nearly downshifted into 2nd instead of 4th since it snaps the gearshift so far over.
In short, for those interested in doing the Type R Ring & Pinion there are two ways you can go: (1) Just replace the ring, pinion and oil pump gears, or (2) Create a more complete R-like transmission and differential conversion by installing the additional 3 parts. Going with the latter option probably makes sense for those doing lots of track driving.
Comptech 4.55 R&P (for 5-speed)
[DH] History: Back in November, my Comptech R&P failed in my car. The teeth came off the big ring gear. The tranny case was also damaged, but luckily my mechanic had my old NSX tranny case lying around that was thought to be in
the "snap ring" failure batch, but it wasn't, so he graciously let me have this case he had been storing. No damage to the short gears.
The failure occured when shifting from 3rd to 4th on the freeway onramp, so it wasn’t like it was under tire screeching abuse when it failed. Comptech didn’t have any more R&Ps, as they were moving to another manufacturer. They were also hesistant about refunding me my money or sending a new R&P, and kinda keep putting off the topic "until the new
R&Ps came in". Having had experience when people say, "we will be getting some new parts soon, but we can't tell you when", I opted to have the stock R&P put back in with the short gears, so I could drive the car, and then think about what I was going to do with the Comptech R&P "warranty" that I felt I was entitled to. True, it is an aftermarket racing part, but I guess many people told me that R&Ps rarely fail.
Every couple of weeks, I called Comptech, and their response was, "The Ring and Pinion has not come in, and we are not sure what we can do to replace your R&P".
Now, let’s move forward three months. Monday – February 9th. I call Comptech, and they got the R&P in! They
said they will send me a new R&P for free! My faith is restored in Comptech!!!!
I also prep my mechanic to be ready, that the R&P is coming. The shop I go to (South Coast Acura) has lost two of three of their NSX mechanics. They guy that is left, Larry, is the guy that has been servicing my car for the past year or so. I also order the Comptech fiber plate for the clutch(the two plates), as my mechanic said that it was down to about 30%
in his opinion when he put my old R&P in back in November. As long as he is pulling the tranny, might as well throw in the new clutch plates, as the labor will be cheap compared to redoing the clutch only 6-12 months from now. I am going to Sears Point in 10 days. Typically, I wouldn't try to put all these parts in, as from previous experience I should be
like a software consultant, and TRIPLE the amount of time I think it would take to complete the job. Normally, I would not want to do ANY mods to my car 10 days before an event because of prior experience, but, my clutch is getting a little on the slippy side, so I said to myself, what the heck, let's do it.
Tuesday – Feb 10th. I call Comptech, they are getting ready to ship. I tell them to ship FEDEX to the dealer.
Wednesday – Feb 11th. I call Comptech. They still haven’t shipped part. I drop my car off at the Dealer, and tell Larry to completely clear his schedule so he can work on my car, because I want it back by this weekend so I can abuse the car and test it out before I drive up to Sears Point (500+ miles) for the Alfa Club Time Trials. Since South Coast is short on mechanics, they usually don’t meet their schedule of when they say the car will be ready, so I tell the service rep and Larry, "screw everyone else, just make sure my car is first in line on Thursday morning to be worked on, as I got a prior reservation."
Thursday – Feb 12th. South Coast Acura still doesn’t have the part. Tim at Comptech says he will personally make sure it gets shipped so Acura gets it Friday.
Friday – Feb13 – I stop by the dealer at 3:00 p.m., to check progress on my car. (hey, if you are in their face, maybe I can make sure my car is the top priority of the day). They still don’t have the part! I am going ballastic, as now the car might not be ready for next weekend….. and we are all getting psyched to go to Sears point. I drive home, ready to kill the Comptech guys. I get home, and the parts + clutch plates are just sitting on my porch. $3500 worth of parts just sitting on the porch for any thieving NSX owner to steal, but I guess is it better that UPS just left them there, so I at least can take physical possession of the parts. I take the parts to the dealer at 5:00 p.m. Friday. Dealer says that they will start the job on Saturday, and Larry will work some overtime on it.
Saturday – Feb 14th – Larry is working on the car.
Sunday – Feb 15 – My mechanic calls Comptech. He gets a hold of someone, to ask them why the R&P seems like it is made out of "soft metal". Meaning that if he puts the Pinion? in a vise, clamp it down, and take it out, the metal seems like it is gets "dinged" and marked from the vise. Comptech says, "hey, it’s normal, it is a racing part".
Monday – Feb 16 – I call the dealer at 3:00 p.m. Tranny is put back together, and he is getting ready to put it in the car. I started to jump up and down in my office, as now I can pick the car up tomorrow and get the rest of the stuff done, like get tires changed out, get wheel balance, get someone to fabricate some customer seat brackets for my new OMP seats.
(I got some discontinued fiberglass Grand Prix OMP seats. I like them!)
4:00 p.m. – Mechanic calls me, leaves message. Says that Comptech called, and told him THEY SHIPPED THE WRONG R&P, and to take it out. I call Comptech, and they said that they shipped the R&P for the Realtime car
instead of the one I was supposed to get. I tell them, "so what, I gotta get my car outta the shop, I got to get wheels aligned, tires put on, new racing seats put in, get brackets for the racing seats made, etc. Comptech insists that the R&P I have won't be warranteed, as it is from a different manufacturer than the new manufacturer that has the part they
will warranty. He also said that the R&P I have will be noiser, as it isn't "polished". I basically told him so what, I gotta get my damn car ready for my once in a lifetime trip to Sears Point with all my buddies, and so far Comptech has wasted 7 of my 10 days to get the car ready. I don't give a shit if it is noisy. Comptech INSISTS that we gotta put the other R&P in it, as they will feel the newer R&P will be more dependable, and since I had problems with the other R&P, he wants to make sure I have the parts that should last. I talked to my mechanic, and we debate whether or not to blow Comptech off and go with what we got, but my mechanic convinces me that we should go with the right part they want to ship us, even if it means losing another day.
Tuesday morning – I start calling around trying to get someone to make some custom seat brackets for the OMP seats. I shoulda figured the "universal" mounts would not work. I call about 15 places, and finally found a place that will work on them Thursday, but they might not finish it until late. I say fine, I will drop off car in the morning.
Tuesday – 7:30 p.m. My mechanic just finishes up the re-re-re-re-install. (since when the first one exploded, he put the stock one in, then he put the "new wrong one" in, and now he put the "new right one" in) . Comptech pays for installation of the re-install (just the last one). We go for a test drive, and it feels fabulous when shifting. Real light,
fast, buttery shifts, both up and down. I leave the car with the mechanic, as I needed him to bleed the brakes, as they felt soft. I have no time to do anything with the car, as I have to work about 65 hours at work from Monday thru Thursday.
My commentary on the Comptech R&P with the short gears I really like it. I mean **REALLY LIKE IT** Since I have driven the car with:
- Stock R&P and Stock Gears (original)
- Comptech R&P and Short Gears (original mods)
- Stock R&P and Short Gears (when Comptech R&P blew up, I drove it like this for three months)
- Comptech R&P and Short Gears(just re-re-re-re-reinstalled last week)
I feel like I can’t live without the Comptech R&P. Here’s why:
- Stock R&P and stock gears - 2nd redlines at 85 mph or so, 3rd redlines around 118 or so
- Stock R&P and Short Gears - 2nd redlines at 72 mph or so, 3rd redlines around 105 or so
- Comptech R&P and Short Gears 2nd relines at 62 mph or so, 3rd redlines at 90 mph or so.
With option 3, virtually everywhere you go you can buzz to 8000 RPMS in 2nd gear, whether you are on the freeway or just your local city streets(if it is safe, of course), and on the freeway you can always buzz to redline in 3rd. I like hearing and feeling the car accelerating to the redline. Every single time I shift, I am conscious of the fact that the car is rapidly accelerating to 8000 RPMs, and I have to go "ah, that feels so good" feeling every time I shift. And I have the R&P + Short Gears to thank for it.
My opinion on the Comptech R&P + Short Gears: Is the R&P faster on the track? Yes, it feels faster, but not by a huge
margin. Let's say it is worth maybe one second a lap for the sake of argument. Is it worth the money?? Well, combined with the short gears, if you:
- Beat the shit out of your car and run it hard
- Like to redline it every shift you get, and have those shifts come up very quickly
- Need to cut maybe a second in your lap times to remain competitive with your buddies
Then I would say you should consider the Comptech and short gear setup. If you think about it, if you DO NOT have the short gears and R&P, how often do you get to take it to the redline in 2nd or 3rd and hear the VTEC engine/exhaust roar? Once every couple of weeks? Hey, I get to do it about 25+ times a day in normal street driving… 🙂
[STH – 99/2/26]
Mine was properly installed by Davis Acura and Comptech will admit it as well; the early 4.55 R&P DOES whine and very annoyingly. I had to blast my radio because the R&P drowned out my exhaust(Comptech billet tip) at cruising speeds.
What Are The Numbers?
[BBU] Many people want the numbers, therefore last night I did some more numerical computer calculations to show the impact of different gearing. The calculation is a finite-difference solution of the energy equation which governs acceleration. The solution includes weight, tire size, horsepower, and of course gear and R&P ratios. In order to go to higher speeds, this time I also included aerodynamic drag and rolling friction. The baseline or stock case is a 91-93 geared NSX with the stock 4.062 R&P, producing 245 peak horsepower to the road, weighing 3200 lbs including the driver. I included 0.3 seconds to complete shifts. Although the exact magnitude of the result may have a little uncertainty, the numbers will allow you to compare different cases side-by-side and make your own decisions.
Just to warn you, the cases that had to shift to the stock 5th gear to reach 140 mph really dogged at the end. The times are heavily dependent on the shift speeds, for instance the short gears by themselves produce the fastest time to 140 mph (in the 1st table), because that speed is very near the redline. This same case is the slowest to 80 mph because it had to shift. But pick the speeds that you think are important and make your comparisons at that point.
In addition to looking at gearing, I included two cases that did not modify the gearing, but instead either added horsepower or reduced weight. The following table lists the time it takes in seconds to reach the given speed.
speed = [RPM x Diameter x Pi x 3600(sec/hr)] / [gearratio x R&Pratio x 5280(ft/mile) x 60(sec/min) x 12(inches/ft) ]
|6 Speed||4.235 R&P||4.55 R&P|| Japanese
+ 20 HP
– 200 lbs.
|Speed 0-MPH||Baseline|| Japanese 5-speed
| Japanese 5-speed
+ 20 HP
– 200 lbs.
Hopefully this will help you decide what modifications, if any, you would like to make.
When accelerating from 130 to 140 mph the six speed would be in 5th gear (0.91), the stock five speed would be in 4th gear (0.967) and the Japanese geared tranny would be in 4th gear (1.033). Therefore the six speed would be the slowest from 130 to 140 mph. The approximate time it would take for each would be: Japanese 4.64 sec, Stock 5.37 sec, and six speed 6.2 seconds. My other point was that the tall gearing of the six speed in 6th gear would lower the top speed of a stock 91-96 NSX. For a variety of reasons, I wouldn’t put a six speed in a 91-96 NSX with stock horsepower. I would pick the Japanese gear set based on cost, top end speed, and nearly equal acceleration. If I had more money, I would definitely go with a 97+ six speed coupled with the additional horsepower they come with stock and need to work best at top end.
[BHA – 99/8/31] When I was deciding what mods to make to my car, the section on gearing performance of the faq was extraordinarily helpful. I refer especially to the mathematical work done by Bob Butler. Even though it shouldn’t have been damn near perfect in its predictability of redlines and speeds, speeds and RPMs, etc. I have found the results to be remarkably accurate from my old (stock 5 speed, 4.06 R&P) to my new (6 speed, 4.55 R&P). So if you want a guess on what gears you have or are thinking of making a change in gearing or R&P, I recommend a thorough reading and understanding of Butler’s work, and some time with a calculator or spreadsheet…
Impressions Of Various Setups
Japanese 5-Speed With Stock 4.06 R&P
[DNG] The transition from 1-2 is not at close as I thought it would be. There was still a significant drop from 1-2, but not as bad as stock. But going from 2-3 and 3-4 is a major difference. It feels a lot faster. I think the RPM only drops ~700 RPM as opposed to ~1500 on the OEM. Cruising in any gears between 2-4, just stomp on the pedal, and it zings. Most people don’t like the 5th gear, but I personally like it. It provides a good cruising gear. I was expecting a ‘bog’
from 4-5, but the transition is quite smooth.
Acceleration is much faster. Usually when I upshift, I don’t feel the car ‘decelerate’ (you know, the split second when you release the clutch, and shift… your head jerks forward because you’re no longer accleration). Now, since I’m acclerating
so much faster, the switch to next gear can be felt much more. Imagine what it feels like for NSXs with TTs + short gears.
Make sure they include the alignment as part of the short gear installation price. Most mechanic will probably just mark the old alignment settings when they take apart your suspension, but Bernie at Davis Acura said that most times, the numbers will be off. When we put it back on the rack, sure enough, it was off.
Japanese 5-speed with Comptech 4.55 R&P
[HS] Here’s my philosophy on gears (and why I like the Japanese gear set with the 4.55 ring and pinion). While a gearset should be optimized for each race track (so the car is "on the cam" at all times, and right at redline in top gear (actually about 500 rpm short of it) at the end of the longest straightaway), that’s impossible with our cars. So, the alternative is to make the gears as *usable* as possible. The "ideal" would be a bit shorter 1st gear (used just for pulling away from rest) and then a six (or more, the more the merrier) speed that had it’s gears spaced closer and closer together as you went up through the box. The top gear should be selected for the top speed the owner is interested in – — and the lower gears spaced accordingly. The 4.55 should give about 165 mph — as fast as I’ll ever want to go, and unatainable at any track on the West Coast (Riverside’s gone, OK maybe Kent in Seattle).
The stock 5-speed gears are just too damn tall for anything except cruising where there are few curves and fewer cops. The Japanese gearset lets you choose among several gears for street driving — a 40 mph curve will let you cruise it in 4th, have a little fun with it in 3rd or "play racer" in second. The spacing is much more even, and therefore "usable" than the stock gears. If the R&P is not changed, the top (5th) gear is way, way too tall. The Downside on the 4.55 — a bit more noise (gear noise), a bit more engine noise (cruising at 70 on the freeway), a bit less gas mileage. I’ll settle for those.
I too have had ‘Merican Iron with 4.11 and 4.56 (even one with 5.11) rear-end gears — the NSX with 4.55 will be nothing like them. Larry Long says that Comptech says the 4.55 "won’t be much help at a track"… Horsefeathers, unless the track is Daytona or someplace with 175 mph straights. LL also says RM says the 4.55 R&P hurts at Buttonwillow — sure, if you’re running the stock gearset. The short gears and 4.55 would be fantastic at Buttonwillow (I’m basing this on Doug’s NSX Files tape, I’ve never driven there — too new).
[BC] I have the short gears plus the ctech R&P. You can go to redline in second gear (about 60 mph) on back roads (vs 80 mph). This makes all the difference in the world in terms of the fun factor. The stock NSX second gear is nice on the highway, but with the modified gearing, 3rd redlines at about 90 mph and takes the place of 2nd for passing maneuvers. 4th becomes the equivalent of the stock 3rd. You often have to buzz along at 4000 rpm in 5th to cruise in the fast lane at around 80 mph, but it doesn’t seem to adversely affect fuel mileage. Oddly enough this modified gearing closely matches that of my Subaru, so it isn’t a radical setup. Entirely practical for the street.
[DH] 23 days ago I dropped of my NSX to get the Short Gears, Comptech R&P, and the Comptech Street Performance Clutch. About an hour ago I finally picked up the car. The reason(s) that it took 23 days is way too long a story for an email message, so I will be posting up on my website FOUR pages about the experience in a week or two.
Initial impression after 20 minutes of driving: Feels like a TOTALLY different car when flooring it and aiming for 8000 RPMs. Acceleration seems much faster in 2nd, 3rd, and 4th gears. The Comptech Clutch grips a lot better, kinda like it "bites" better than the stock clutch.(someone on the list mentioned that the Comptech Clutch is made by Centerforce, I don’t know if it is true or not). The clutch pedal feel is the same, but you can feel it really gripping when shifting between gears.
A couple of the mechanics were buzzing the car around before I got there, and both agreed that it feels dramatically different from the stock NSX five speed, and felt that it was mod that they could really "feel the difference".
Only disadvantage that I can tell so far is that I no longer can go 65 miles per hour, downshift into 2nd gear, and accelerate to 83 mph in 2nd. That was always kinda fun to do when needing to pass someone on the freeway.
[MN] THIS is how the car should have been made in the first place. Is normal drivability affected? Definitely! No more bogging in second gear, no more bogging in third gear, etc. Now I must work on my 3-4 shift.
However, if you stay out of the throttle, you can still bog and lug the car around town all day, no problem. But even if you’re lugging the car at low speeds, it is still WAY smoother, because of the close ratios of the short gears. BUT, when you mash the throttle, HOLD ON !!
Remember the Doug Hayashi drop into 2nd gear on the freeway at 60? Come ride with me as I drop it into 3rd gear on the freeway at 70 !! However, again, if you stay out of the throttle, the RPM difference in 5th at 70MPH is only 300 RPM ! You don’t notice the difference, it only feels "crisper", or, like the car is much lighter.
And you know how you can be cruising down the road in 2nd at about 4 grand and "blip" the throttle and get that neck jerking acceleration ? Well, you can now do this in *third* gear, with better results !
[HS – 99/2/25] I believe I was the first on the list to do both the Japanese gears and the Comptech R&P (3/19/97). I’ve had zero problems and highly recommed the combo.
Comptech 4.55 R&P
[BC] I had the Comptech R&P installed about a year ago along with a carbon kevlar clutch (from Fodge and Peck Motorsports – FPM). I’ve driven 20k miles since then. Performance improvements noted:
1st gear – a bit more kick, nothing astonishing
2nd gear – if you upshift from 8000 rpm in 1st you will notice you no longer have a sluggish sensation. The car feels much more lively, about like the difference between carrying a passenger and driving solo. 2nd also becomes a better back road gear. Cruise at 40 mph in third then downshift to 2nd and rip it up to 70mph in a few seconds. (I’ve also noticed that even though the starting revs in second are below the VTEC threshold, if you catch the 1-2 up-shift just right the car can stay in VTEC mode, as if the ECU has a time delay for switching the cams when you cut the throttle to shift which is just long enough to allow you to get the revs up… either a bug or feature)
3rd gear – again, the up-shift from redline in 2nd feels less sluggish. Most significant improvement you’ll notice is cruising the highway at 70mph in 5th, downshift to 3rd and you’ve got immediate VTEC for passing.
4th gear – a bit closer to VTEC mode at highway speeds and more usable for passing non-competitive obstructions.
5th gear – theoretically allows the engine to pull to redline at 166mph, I haven’t had the chance to test this though.
Generally the car will also feel like a "normal" five speed. I’d gotten used to the ratios of my MR2 Turbo and Rx7 R1, the NSX felt more familiar after I changed the R&P and the speeds in the gears became more reasonable (dropped about 10 mph).
The primary downside of the R&P is that it is noisy. For the first 10k miles after installation the ring & pinion gears were very noisy but they seem to have quieted down recently. You’ll hear significant gear whine at cruising speeds, making the car seem a bit… coarse. The noise hasn’t changed much in 20k miles. When I had the stock muffler back on the gears seemed very loud, but when I went back to the Supertrapp it just blended with the background drone, but then you know how loud a Supertrapp is.
Overall the performance increase of the Comptech R&P alone isn’t anything stunning, more like an incremental improvement in the manner of headers and mufflers, but it all adds up to give the car a feeling of lightness and responsiveness.
All Of The Above
[MJ] If you are happy with the stock gearing, then yes, you will notice the difference, and it would be OK to not do the shortie gears, but since you have it all apart already why not throw them in ? (I do not sell the gear sets so I am not plugging them just to make a sale) it is similar to bolting on a set of headers OR an exhaust. Each gives you ~8-10HP. It is noticeable, AND both of them together make more of a difference than one or the other separately – it is more like fine tuning than adding NOS – if you know what I mean. The R model in Japan comes with both the "gears" and the R&P standard and I think the car now feels like it should have when I bought it. (the shortie gears can be done for less than $1000 parts and the majority of the labor is taking it all apart and reinstalling everything anyway so installing the actual gears and R&P parts are a negligible part of it)
4.55 pros: faster acceleration (very noticeable) = short term fun. (except for Harry of course who wants a 5.11 <G>)
4.55 cons: (depends on your POV) not cheap ($2800.00). Reliability/quality control concerns. "Buzzy" (I cruise at 3500-4000 rpm – do I want that to be ~4000-4500? not with my muffler I don’t). Shifting all the time. Possibly reduced mpg due to higher rev’s. Some of them were noisy.
4.235 pros: cheaper ($1000). OEM quality because it is OEM. "Livelier" feel (not neck snapping, but like you removed all the spare tire/tools/cats/headers & that overweight ‘instructor’ you were hauling around the track etc. and now you can GO! <G>). Not noticeably "buzzy" (3500 rpm turns into 3660 – not that much louder). No new noises at all.
4.235 cons: May be hard to get. Not enough of a change for some people.
6-speed with 4.55 R&P
[BHA – 2000/3/29] I have a 92 with a Comptech 6 speed tranny, power grip clutch and 4.55 R&P. I normally get around 20mpg in the city and recently got 27mpg on the highway on a longer trip, cruising most of the time in 6th around 70mph at 3100 RPM. I usually plan on 300 miles per tank in the city and 400 on the highway.
[DG] Plan on $850 parts, $1000 labor (unless Acura happens to goodwill your snap ring repair, which most can’t count on, in which case subtract about $600) for the Japanese 5-speed gears.
[LL] A small clarification of Bruces’s post that some may be wondering-you don’t have to put the stiffer R shifter spring in, it’s optional. The torque sensitive limited slip differential was put in starting in 95, the 95-97 cars need to put in the older 91-94 differential to use the R parts.
[BV] I picked my 96 up today. As I reported early since the installation of the short gears, 1st was difficult to engage and the rest of the gears felt significantly "notchier". The mechanic changed a couple of shims on the mainshaft and now it shifts perfectly. I think it would be wise for anyone adding the short gears to make sure the person doing the conversion is up to speed on this shimming issue.
You must log in to post a comment.