eyeball kid

I have a line on a good trans (sub 100k) with an R/P that has been checked out by a local and trusted shop. The tranny is from a 944s and I can get it for around 400. I don't need it per se, but I'm game to stockpile desirable parts. Is this an upgrade with its closer ratio or not?

jstand22

yeah it would have better ratios for the Turbo (I assume your car is a Turbo, because you're posting in the Turbo forum), however the S ring and pinion can't handle the power the turbo has, it probably wouldn't last too long before self-destructing.

jasonlp

+1

rebuilding my turbo tranny and my n/a r&p was missing chunks out of the teeth still ran perfect just super rattly and loud

eyeball kid

Thank you--yes 88 951

dillon410021

I am waiting for a guy in my town who has a ls2 with the stock 944 trans to blow up! That LS2 is too much power for that trans, but It is very fast.

Van

I believe the 944S has the same R&P as a 944 - which the 951 will shred in short order.

But, what the S trans does have is a shorter 5th gear, which lots of people find desirable.

jasonlp

+1

I'm going for S2 this time around as I have almost double the original hp/tq. For a k26/6 and k26/8 the s/na 9.35 r&p worked great for me. Only reason I had s/na r&p to begin with was that the s2 didn't exist yet.

r&p's
s2-8.31
turbo 8.27
s/na 9.35

eyeball kid

So if I'm planning on keeping it under 300hp and maybe doing some auto cross DE events occasionally, is this a good box to get? Could I get a quaife for it?

Van

Some people may luck out for a little while... But you're courting danger.

the R&P gear teeth are physically smaller on an NA box. A 300 HP car (if you use the power) will shear the teeth.

ehall

I thought special tool ran the S box on his car. Did he not?

Oddjob

ST ran/runs an S2, not an S trans (R/P).

Probably can come up with some various threads on this topic by searching both the Turbo and 944 boards.

N/As can and do somewhat often break N/A R/Ps (with 150 hp) - never use an N/A trans in a turbo for even for street use.

S R/P is the same ratio and tooth count as the N/A R/P but they are not identical parts. The S R/P is somewhat stronger than the N/A. But with that said, its still not strong enough (even a stock k26/6 car has nearly 50% more torque than a 944S)....

Its been relatively common knowledge for years that a turbo will break the S R/P. I think there was even a Porsche Tech Bulletin saying dont do it, and I remember tech articles in Pano going back to the late 80's, maybe 1990 telling of known failures of the S R/P installed in Turbos.

If you want to screw around with a cheap S trans, and throw it on to see how you like short ratios, knowing that you will eventually break it, go for it. But it wont be a long lasting trans for an auto-x or DE car. Probably not much of a safety concern on an auto-x course, but I would not want to lock up a trans on a high speed road course.

If you want shorter gearing, put in an S2 gearbox (swapping in the .829 Turbo 5th is optional), or put the S2 R/P in your turbo gearbox.

Olli Snellman

S box is the closest thing to 951 box, if you want to use a N/A box. It's not the same as "normal" 944 N/A box. Another good N/A box would be a special Switzerland only S2 box, but i suppose that would be hard to find in the USA.

Oddjob

The S, S2, and Turbo transmissions are the same casings, bearings, synchros, etc. Most of these components are not interchangeable with the N/A gearboxes.

The S and Turbo have identical gear sets R, 1-5th. The S2 has a taller 5th (.779 instead of the .829). The R/Ps are the big differences here. As I said above - not a good idea to run an S R/P (3.889) in a turbo. The S2 R/P (3.875) is very close to the same ratio as the S, but has fewer and larger teeth (8:31 vs 9:35) - and has proven to be strong enough to hold up even in higher powered Turbos.

If you want the "short" 5th (S/Turbo .829), you can either add an S2 R/P to a turbo box, or swap in the turbo 5th into an S2 box. End up with basically the same thing, so the costs of either option will drive the decision.

One additional note on that: the S2 gearboxes have the same input shaft and LSD (if equipped) as the Turbo S AOR transmissions, so they have the hardened teeth for 1st and 2nd gears and the thicker friction discs in the LSD. This may also factor into the decision.

eyeball kid

Thanks. I think I'll pass on this box and wait for either an S2 or good turbo one to come up.

josephsc

FWIW, I've been running a S tranny with a 968 motor for the last 4 years. I thought I'd grenade it right away, but I'm still waiting. It does have LSD, which might make a difference.