Special gearing on a 5-speed gearbox

[gheba_nsx]

As some of you may know, I sold my silver NSX and I bought a black one. One of the nice mod that was done to the car is the fact that the 2., 3. and 4. gears were changed with post '97 parts.

Here are the ratios for the different speeds on the OEM 5-speed and on my modified gearbox.


1. - 3.071 -- 3.071
2. - 1.727 -- 1.96
3. - 1.230 -- 1.43
4. - 0.967 -- 1.12
5. - 0.771 -- 0.771

FYI, the OEM 6- gears has 0.910 for the 4th and 0.720 for the 6th gear.
Having the original 5. speed allows the car to still reach the same max. speed that was possible with the OEM 5-speed gearbox.


The feeling when changing gear near redline in 1., 2. and 3. gear is a lot nicer than when I had the stock 5-gears. After the upshift the revs are higher (about 14% higher than before) and the "gap" before the VTEC range is reached is a lot shorter (if not disappeared...).

0-60 should be improved of about 0,3s from what I understood reading the table that was on a old NSX-driver magazine using 6-speed vs 5-speed when used with the 3.0 liter engine.

The only drawback is that the acceleration above 130 mph (when going from 4. to 5. gear) is worse. But this is something I can live on since the "fun" normally is below that speed.

Anyway, how could I measure how much slower is the car from 130mph to 170mph?
Is there a way to measure this using the ratios here above?

Thanks a lot for helping!

 

[Enzo]

Anyway, how could I measure how much slower is the car from 130mph to 170mph?

Come for a little race against my NSX on a long straight road and you will have the answer !

 

[gheba_nsx]

And I thought that hiding the post inside the Tech forum would have kept out the trolls!

 

[nsxtasy]

how could I measure how much slower is the car from 130mph to 170mph?
Is there a way to measure this using the ratios here above?

Bob Butler could run your gear ratios through his mathematical models to do the calculation. However, acceleration above 130 is MUCH slower than below 130 (for example, acceleration from 130 mph to 150 mph typically takes around 15 seconds with any of the gearing options), so measuring it is really not all that meaningful.

 

[ak]

This is a very interesting idea. This will keep the highway driving the same but 0-130 acceleration same as 6 speed. Thanks for sharing! I would not worry about 130+ acceleration either since most track, you wouldn't go faster than 130...

Now on the FAQ, top speed of 5th gear in 6 speed is 155mph.. So I wonder how buzzy it'll be if you just use 1-5 gears of 6 speed in 5 speed.

-ak

 

[JoeSchmoe]

I thought the first 2 or 3 gears were attached to the mainshaft.
Does this mean you are running a '97+ single plate clutch as well?

 

[gheba_nsx]

Ken, yes I think you are right, my was only a theorethical question. But I assume the difference wozuld be quite noticeable...


JoeSchmoe, I really do not know. The work was done almost two years ago and costed quite a lot of money (parts were ordered directely from Honda).

The clutch question is interesting, I should ask the mechanic...

 

[gheba_nsx]

Small update: the previous owner does not know if the clutch is single or dual plate. But it has been changed (maintenance) at the same time of the gears swap so it ,may really be dual plate (will call the mechanic next week).

Anyway, the first gear was changed together with the other gears (the first and second are really attached to the mainshaft and he has still part lying in his garage, JoeSchmoe was right).



I thought the first was not changed because the ratio is still the same as before (pre and post '97 have both "3.071").

 

[JoeSchmoe]

Small update: the previous owner does not know if the clutch is single or dual plate. But it has been changed (maintenance) at the same time of the gears swap so it ,may really be dual plate (will call the mechanic next week).

Anyway, the first gear was changed together with the other gears (the first and second are really attached to the mainshaft and he has still part lying in his garage, JoeSchmoe was right).

I remember the splines on the mainshaft being different between the 5 and 6 speeds, which is why you cannot easily swap between the single and dual plate clutches.

What's puzzling is if you are using the 6 speed's mainshaft and its compatible with the 5 speed, where does the 6th gear go? If someone has a 97+ service manual, can you please post the gearbox parts breakout diagram?

 

[gheba_nsx]

Ok, puzzle solved!

Maybe it could be added to the trivia & FAQ...


The previous owner was not very clear what he did pay for when he bought the 2,3,4 gears.


In Europe, 1995 and 1996 model year NSX did get the following gear ratios:

1st gear (3.071)
2nd gear (1.952)
3rd gear (1.400)
4th gear (1.033)
5th gear (0.771)

also a new 2nd, 3rd and 4th gear (1st and 5th remained the same). By coincidence ( ) these are the short gears described in the FAQ.

In 1997 they got the normal OEM '97 ratios. I checked all this with him on the Honda part book together with the mechanic that did the work.

What the previous owner installed are also the short gears and not the '97 2nd, 3rd and 4th.

These are very close to the '97 so teh result is about the same... in other words, I LOVE THEM!


PS: is the same in the US? Or did the '95-'96 (early targa models) get the "old" OEM 5-speed gears? I was explained that this was done to add some sprint to the heavier cars.

PPS: is the NSX-R (old, 1993 model) using the japanese short gears?

 

[nsxtasy]

PS: is the same in the US? Or did the '95-'96 (early targa models) get the "old" OEM 5-speed gears?

Neither. In '95-96, the U.S. cars changed to a second gear that was slightly shorter than before, but not as short as the Japanese gears. The other gears were unchanged. Check out the ratios in the FAQ here.

PPS: is the NSX-R (old, 1993 model) using the japanese short gears?

As noted in the same section of the FAQ, the five forward and one reverse gear in the NSX-R was the same as the regular JDM NSX, but the NSX-R used the 4.235 R&P instead of the 4.062 used in all other stock NSXs.

 

[gheba_nsx]

Thanks, right after posting I went and did check the FAQ...

Nice that you answered and not your good friend the Nazi!

 

[daveh]

Hey there Joe,The late clutch fit's just fine in the early car's .The last 4 clutches I've done on early cars I've put the single disc in.It costs a lot more maybe $3k intead if $2k,but from an installation stand point it's a lot easier .I just did a trans O/H on a 2000T with 7k on it and kept all the old parts.The bummer is the dual mass flywheel can't be refinished but hopefully if you don't fry it you can just replace the $300 dollar disc next time around.That's my plan anyway .Hey joe if you're in the valley cruise by and show me your car .I work @ Stevens creek Acura.Lets' compare.Later....

 

[JoeSchmoe]

Hey there Joe,The late clutch fit's just fine in the early car's .

Good info. So the splined portion is shorter on the 6 speed mainshaft right?