sumpcracker

Hi,

I had hopes someone could shed some light on this unusual swap.

I am wondering how this swap would alter the cars performance?

I have a 944T, around 420hp (flywheel) and run a dogleg 931 euro trans.
I love that i can launch the car without worrying about diff breakage, but the slow often crunchy gear selection is being a bind for daily use.

I cannot find the ratio compariison/speed per gear for the euro 931.

Also, shorter gears my actually hamper the performance due to not making full use of the boost curve/torque?

As my car is now, it is dead even from 60-150 with my friends car, it would upset me if this modification allowed him to pull away.

V2Rocket

This guy might be able to provide you fresh synchros...
http://garage.ideola.com/prod-ClutchTransKits.html

Dimi 944

Do you launch the car in 1st and 2nd gear or do you do rolling start?

If you are launching the car at low gear I would not recommend a 944 transmission. You will destroy it pretty quickly. I have seen and worked on a few destroyed turbo transmissions from launching or the V8 torque. S2 and Turbo transmissions have the same gears except the final drive. The S2 has shorter final drive. The Turbo S has additionally treated 1st and 2nd gears but I still wouldn't use it for launching application on high HP car.

My recommendation is the G31 931 or G44 968 transmission. They use the same diffs and have similar, stronger than the 944 trans, gears.

I can do a speed comparison for all transmissions for you and have some in stock too. Shoot me a PM.

sumpcracker

I do launch hard from 1st somtimes, mainly because i know i can with the G31, i would never do this if i fit an S2 gearbox !

I would love the smooth shift of a 944s2 box, but you guy seem to be leaning on me keeping the G31 in there?

Forgetting launch, is the a Chance that say 60-150 im going to lose some time wth the S2? The G31 does have ideal ratios as it is.

Dimi 944

What is your rear tire size and usual upshift rpm?

morghen

Strangely enough for this topic I have two 924 turbos, one with a G31 and one with a 944S2 gearbox
Yes the S2 box feels more precise and a tiny bit faster perhaps but i think a freshly rebuilt G31 will shift just as fast.
The turbo that runs the S2 box has a K27 hybrid turbo on 1.1bar and until now no gearbox problems...tho it minced a 944NA gearbox once going up a bridge...but i never abuse the car, never really launched it and stuff like that.

However, the S2 box is actually shorter than the G31..or at least mines are like that...My G31 could have been messed with since that car belonged to a racing club in UK for some years...but check the numbers to confirm this.

I have been driving the G31 to work as a daily for weeks and its a lovely gearbox. I love it and in the future i might ditch the S2 box from the other car as well if i find a good G31.

Rebuild your snailshell, replace the linkage bushings and joints and it will shift properly and fast.

Dimi 944

The following are the speed at upshift RPM of 6000 and the RPM after upshifting for US/Canada spec G31 vs S2.

G31 S2
Gear Speed Speed
1st: 28.22 31.06
2nd: 50.26 52.80
3rd: 73.40 77.65
4th: 95.98 105.14
5th: 148.93 139.73
RPM RPM
2nd: 3368 3530
3rd: 4109 4080
4th: 4589 4431
5th: 3867 4515

The G31 seems to have shorter gearing.

morghen

Except 5th gear that looks longer on the G31

fasteddie313

US G31 has the really high 5th for fuel economy purposes.. Euro does not..

sumpcracker

Thanks guys, the gearing looked like it would suit my set up, so I fitted the S2 gearbox, tube and beam. I hate that job, gearshift is nice now, I just need to remember not to go hard in 1st.

morghen

what did you do with the G31?

Raceboy

Did someone say not to launch hard with S2 gearbox?

ideola

G31 will never shift quickly or smoothly, rebuilt or not. I have converted almost all of my cars to the snailshell because I love the character of it. My only non-snailshell cars now are the 88 SE, the 77 Martini, the 78 LE Auto, and the 81 Weissach.

I *hate* the US-spec long 5th gear. The Euro gearing is sublime.

If you want to race or enjoy "motoring" stay with the G31. If you want a more modern, carefree shifting experience, go with the Audi 016-based box.

Dog rings are once again available on my site, and we have just commissioned replacements for the NLA G31 mid-housing gasket. Not all of the G31 stuff (rebuild kits, synchros, etc.) are back on the site, so PM or email me if you have interest.

sumpcracker

I already regret the swap, the gearing was better and the car felt better with the G31 in it. car feels a bit less serious. Better in traffic now tho and my girlfriend can use the car, there is an art to a G31.
I miss the careful slow selection into 4th and feeling 1.6 bar pull it like a MF, the gears were clearly developed for a boosted car.

The 931 gearbox is now in Romania.
I think the car will be more comfortable now when I take it to Poland for the summer as its a lot less stress at lower speeds.

333pg333

Never driven a car equiped with the 931 trans but have owned 951's with the S2 ring & pinion swap into the 5 speed and that really wakes the car up. Bit short final drive for hwy cruising (always wanted an extra gear) but around town, mountain roads, racetracks, it's a great conversion. I really enjoyed that gearbox. Much more than the 968 6 speed that we have in the racecar now...unfortunately.

Video of that car and gearbox on the track back in 2010 having fun with a Modified Evo. You get a pretty good idea of the gearbox ratios in this video.