NCLA951

I like the idea of shorter gears, 5th is too long currently to be great coming out of turn 9 at willow, and I don't need the top speed (149 at 6500 with AGR is plenty for track, and getting there faster is good). Is the R and P strong enough for a mildly built 2.5, 325ish at wheels?

odonnell

That's a 944S trans right? Same R&P as the normal NA. You know about the rest.

lart951

To compare the transimissions, all the info you need on this is in the factory manual sets, in the transmission section and in the turbo supplement. It explains the differences in components and then it can also be checked in PET by referencing the part numbers to the case codes.

944S Trans: AGP and AGR codes (w/o LSD and w/ LSD)
944 Turbo Trans: 5P (w/ cooler), 5R (cooler and LSD), UY (standard), 9U (no cooler, LSD)
944 Turbo S Trans: AOR
944S2: AOS, AOT (w/o LSD and w/ LSD)

The cases are the same for the 944S, S2, Turbo and Turbo S. The 944 n/a has a different case number than these others (probably some internal machining differences)

The gear carrier (black cast iron section of the trans) is the same for the 944S, S2, Turbo, and Turbo S. The 944 n/a has a different part number than the others.

The input shafts for the 944S and 944 Turbo are the same part. The Turbo S (AOR) has a different input shaft (this is the part with the extra hardening process performed on the 1st and 2nd gear teeth). The S2 transmission came with the same input shaft as the Turbo S, and all previous input shafts (for the 944S and Turbo) supercede to the AOR input shaft. So if you went to a dealer today and bought a new input shaft, the only one still available for an S, S2, Turbo, Turbo S is the one with the hardened 1st and 2nd gear teeth. But, Ive never heard of anyone ripping the teeth off the input shaft in an S or an early Turbo, so Im not certain how critical the hardening is.

The gears for a 944S, S2, Turbo, and Turbo S are all identical for 1st – 4th. The S2 has a different 5th gear – its slightly taller than the other cars to give it a higher top end with the shorter R/P.

333pg333

Go for the 951 5 speed and swap in the S2 r&p. Et Viola!

lart951

Yes S2 is the best I agree

NCLA951

I'm guessing S2 RP is stronger then?

lart951

Yes same hardened gears as the 88-89 turbo S AOR

Last two AOT's I sold went north of 3k

333pg333

Yes, stronger but also shorter final drive. Makes the gearing similar to S2 gearbox. Really livens up the performance. Been tested on many modified 951's down here. ;-)

Oddjob

As mentioned by others - The 944S 3.889 R/P won't hold up in a Turbo over the long term. The S2 3.875 R/P will.

The S2 trans has the same gears and parts (bearings, synchros, etc) as the Turbo S trans, other than 5th gear and the R/P ratio.

Since you're talking track use, you'll want LSD and likely the short .829 turbo 5th gear. The oil cooler loop is also a plus. So, often the best option is to either install an S2 R/P in a Turbo LSD trans (so it will have the shorter .829 5th gear set) and cooler (5R or AOR trans), or to build up an S2 trans with the turbo 5th gear. Issues with building up an S2 trans is that the AOT trans (LSD) is rare compared to Turbo LSD transmissions, and the S2 trans was not available with a trans cooler.

lart951

I was just talking to Sid (blown944) i sold him a agr a few years ago to test in his drag car this is what he said:

NCLA951

I'm sitting on a 5P that I was going to put an LSD in, but young child has that $$$ now, and this is cheap enough to do now not some time in the future, and I like now. The AGR has the shorter 5th gear and factory LSD. If I break it or it's too much shifting I'll just get a 5R or do what I initially was going to do down the road.

Thanks for all the input!

lart951

Probably it will be best to install the LSD from the AGR into the 5p I think there is a write up here on the list

Raceboy

You will not break the 944S gearbox unless you plan doing drag starts with launch control.

Dimi 944

Based on your application a low mileage, well maintained AGP or AGR (944S) transaxles with added cooling would more than likely hold up. What could kill the R&P on these transmissions are​ shock loads (dumping the clutch, lifting a wheel, abrupt shifting, etc)
Running lighter and narrow wheels/tires would help the longevity too but that is just the opposite of what most track cars are running nowadays.

NCLA951

Well it's not a track car exclusively, and I only run 225 tires all around, which with RE71Rs is enough for now. I never dump the clutch, but I do drive it hard after it's off the line, and shift as quickly as I can in spirited scenarios. And there is the potential for rapid autocross starts. My only worry about the AGR is the R and P failing, which some sources say is inevitable in a turbo, but other people I trust say it's fine.

I could just wait, find S2 R and P, install that with an OS Giken and have the 5P rebuilt, which would probably be the strongest and best option, but it's also near 5k to do, vs installing the AGR and filling it with swepco, which is obviously significantly cheaper.