View Full Version : S15 6 Speed tranny? Crappy or not so crappy?

12-04-2005, 01:09 PM
I was offered a S15 tranny not so long ago and I turned it down because I had heard many of the S15 guys swapping their tranny for the 5 speed. Does anyone know why they are not liked?

Gear ratio, fragile, fitment?

12-04-2005, 01:50 PM
The 6 gears are in the same space as the 5 speed so the gears are thinner and not as strong so the big power guys avoid them.

12-04-2005, 03:35 PM
The S15 tranny is still a good gearbox, it just can't hold as much power as the S14/S13 5 speed tranny. That does not make it a generally week transmission. If you are planning on having mild mods and not aiming for a 400hp+ car, the the S15 speed would hold it's ground.

12-04-2005, 04:28 PM
Plus you have to adapt a VSS over in order to have a working speedometer.

12-04-2005, 05:32 PM
The S15 6-speed is very weak, as previously mentioned. Most guys wind up breaking them with MILD builds over here...350Hp will break that POS. It's too bad. However, NISMO has a 6-speed crossmission available if you want to drop $4,000. You won't be able to have a speedometer either unless you can rig something, as the S15 speedometer reads off of the diff.

12-04-2005, 07:56 PM
Grex offers a 6spd conversion kit for about $2800. Pretty nice from what I've seen.

12-05-2005, 10:43 PM
i will be surpassing the 400hp mark soon with neary a problem with the tranny.
my spedo works and i have the full s15 swap

12-06-2005, 08:43 AM
Your speedo works because you have the entire S15 setup. People using just the 6spd unit behind an S13/S14 SR don't have that luxury.

12-06-2005, 07:41 PM
Yeah I had a friend break his 6 speed with under 350whp and some fairly hard driving. Another thing to think about is the flywheel funky dual mass pos.

12-12-2005, 05:17 AM
Just to clear a few things, it wasnt stated like this in this thread but when I first heard about S15 tranny being weak, I heard it was weak because it was 6 gears inside a 5spd case. In actuality the S15 tranny is a totally different tranny. Manufactured by Aisin, it is the same 6spd transmission used in the Miata, RX8, Toyota Altezza 4cyl 6spd and a few other cars. It's also a 3 piece tranny, ie: [true bellhousing + front casing + rear casing]

I cant speak from experience with it, but it cant be much worse than the normal S13 S14 S15 transmission which also like to break with abuse. For a track car it should be fine, for a drift car it will break. The guys in Japan who swap them are drifters or drag racers.