VWaddict

Does switching the S2 R&P into a 951S transmission alter the final drive ratio or does it remain the same?

Cheers,

Keith

333pg333

It certainly does. Makes it shorter. Unless you have uber hp it's a great conversion for most people I believe. The stock 951 'box is very long and sometimes hard to feel like you're in the right gear when going fast and slow. It will bring your top speed down a bit, but it's great around town and on most tracks unless very high speed ones, plus it's a stronger part.

Waterguy

951 R&P = 3.375:1
S2 R&P = 3.875:1

About a 15% reduction in overall gearing. I hadn't heard that the S2 was a stronger part than the 951 R&P, though.

VWaddict

Yeah, mine has it installed, and I knew that it was stronger, but didn't know about the ratio difference.

-So on my 951S the top speed has now come down, I suppose?

And I'm also assuming that the speedo over-reads a little also?

Keith

Oddjob

S2 R/P is stronger than the N/A and S. No matter what you hear, it is not stronger than a Turbo R/P. Take a look at the two sets side by side, and the 8/27 Turbo ring and pinion teeth are quite a bit larger than the the S2 8/31 - and when it comes to material strength, size does matter.

Speedo pickup senses the output shaft speed, so it will remain as accurate as it was with a Turbo R/P.

daigo

I suppose a place like Sunset Porsche in Oregon would be a good source?

porschefig

I don't understand this "upgrade"? Would this make the gearing somewhere between 944 n/a and 951 gearing? Can you still go 60 mph in 2nd?

Waterguy

- 15% lower gearing means 15% faster acceleration in each gear, good for tighter track and autocross applications

- It gives you 944 n/a gearing, but with a lower 5th gear than 83-87 US 944 n/a

- You could just barely hit 60 mph at the redline, instead of the 68 mph you should be able to hit with stock gearing, and top speed is reduced to 150 mph (which is faster than I have ever been on a track yet)

333pg333

Yes I actually thought after I entered this info in at 4.00am, that in fact the S2 would not be stronger than the Turbo. It is stronger than the S cw&p as my mechanic confirmed this after destroying his one and going to the S2 version. Not sure about the size of the one in the 968 though, but it won't fit in our box's anyway...more as a comparison.
Oh, and if you're after something purely for 0-60mph, you won't get there in 2nd gear, just under.

IPSC

S 2 ring and pinion ! ! ! WANT WANT WANT ! ! ! yep an S2 ring and pinion is on the acquisitions list. I have yet to talk to anyone who has done this who did not love it. Yes this is better for tight track, autocross and street apps and I think it will do me just fine in DEs. In addition I have heard that the top speed is closer to 160 than 150 HP depending. Still plenty damn fast.

IPSC

VWaddict

My PO tended to only do sensible upgrades, and his (and my) mechanic assured me that they ARE most assuredly stronger than the turbo... His opinion seemed to be that the turbo S transmission -with its oil cooler and hardened 1st/2nd gears- would be better with the S2 R&P, so it was installed while the tranmission was dropped for a clutch change, if I understand correctly.

I wasn't sure about final drive ratio (hence the question), but 162MPH x 3.375 / 3.875 = 141MPH, so if the original top speed was limited by engine rev limit and not load factors, I'd expect the top speed with a 15% reduction in final drive to be rather closer to 140...

Certainly, 1st gear goes by VERY quickly!!!

Keith

Mike Buck

I bought a used S2 trans with the same idea in mind, to install the R&P in my spare 951S trans. When my wrench pulled the diff cover plate on the S2 trans it was ugly. Hardly any teeth left on the pinion shaft lol stock class i stay i guess

333pg333

Perfect for what you want there! If you want to get picky, you may find that in some corners that you are out of the perfect gear for that one compared to the stock box, but that's just the luck of the draw. You will find more often though that you're in a better area of your power band in my experience. Unless you want to start changing out gearsets to suit different tracks this is always possible. When you have some extra mods ie higher hp, you will zing through the gears, but I find that fun.

Waterguy

Depending on speedo accuracy, probably, since our speedos all seem optimistic. However, it is 150 at stock rev limit and with stock tire size. If you raise the rev limit to 7,000 rpm and have the breathing improvements to support it, then I am sure that 160 is possible.


162 mph is drag limited, not rev limited. I have assumed that 150 mph would be at 6,480 rpm rev limit.

gt37vgt

well as for strength I'm sure both parts are constructed very similar but you will generally be transferring less torque through your gearbox out put shaft and more torque through your half shafts. so you are less likely to break a gearbox part and more likely to break a half shaft than the 951