v944

Hey guys, I have a 1986 944 turbo. Some time ago by accident I lowered compleatly my rear which caused my transmission oil cooling line to break, I exchanged it with another one hoping it woun't hapen again, but it broke again. Ok, so I fixed the ride hight, but now I have to spend another $200 - $300 for another transmission oil cooler line. The question is - what is so special about those transmissions - why does it need that cooler loop? to my best knowledge starting '89 944 turbos don't have that cooling line anymore. Is turbo transmission different from regular 944 transmission? I have a '87 944S transmission laying around - can I put it in to my 951 (without it causing any damage)? I would think that they must be the same.
Any helping advice is greatly appreciated.

M758

944S box will fit just fine. However it has different gearing and weaker ring and pinion. It shoud actually make the car feel faster... At least till the ring and pinion fail.

doabarrelroll

The gearing on the 944S transmission is actually identical to the turbo. The only difference is the final drive ratio S -> 9:35 (3.889), turbo -> 8:27 (3.375).

v944

Hey Joe,
So how would I feel this difference in gearing or gearing ratio, or will I feel it at all? also ring and pinion - are they much weaker? what might cause the failure? And at all would you recomend going this route or should I just get the cooler line?

Rob

You will defiantly feel the difference in the gearing and the car will be much quicker and drivable off boost. The ring and pinions in the non turbo and non s2 transmission are weaker and prone to break under the increased torque of the turbo. If you have the trans sitting around and don't mind the getting stranded when the pinion breaks, I would throw it in and see how long it lasts. In my opinion, the gearing change is one of the best mods you can do to a DD turbo. That's why some people run an S2 transmission, because it has the same gearing as the n/a cars but with the stronger ring and pinion. I loved having an s2 transmission in mine.

v944

Hmmm... ok, I don't mind taking transmission off and putting back on, let's consider I would not mind to take it apart, I just looked ap on a diagram - ring and pinion look the same from both transmissions - ARE they the same as fare as diameter and size? would that be an option to take my ring and pinion from turbo transmission and putting it in to 944S transmission? In that case I would kill two birds with one shot: Having a quicker tranny with strong enough ring and pinion

v944

ok, so after doing some research I see now that ratio difference is in the actual ring and pinion... so is that mean that diameter and size would be different, or just amount of teeth on the gears would be different. If the diameter and size are the same - I guess I could put the turbo ring and pinion in the 944S transmission...?

doabarrelroll

I have no idea how that works, but, if you do decide to combine gearboxes, let me know. I have my old S transmission still and I'd be interested to do that.

Van

Not true. All Turbo S cars ('88 S and all '89+) had the cooler.


Your turbo will sheer the teeth off the ring and pinion. They're smaller than on the turbo (or S2) box and can't withstand the extra power.

Oddjob

As mentioned, an S trans (r/p) in a turbo will not last forever. Will be a function of how hard you drive it and how much torque your turbo motor makes. May last 40k miles, may last 4k.

The S transmission case and internals are the same as the Turbo box (other than the R/P), unlike an N/A trans. So you can swap the turbo r/p into the S box - but why? The cost and the time involved w/ replacing bearings, seals, and correctly shimming the differential and pinion bearings for lash and preload is very, very significant compared to replacing a broken cooler loop.

If you want the shorter final drive, do it right and get an S2 gearbox.

v944

The reason why I was thinking going this route is because I already have both transmissions and all that would be required is work. But on another side - I did not consider as you mentioned all the effort involved with replacing bearings, seals, and correctly shimming the differential etc.