TRANSAXLE
1st & Reverse gearsets-
The 1980 Turbo transaxle is a 5-speed Porsche built unit unlike the Audi units used in the rest of the 924/944 line. The Porsche unit is quirky with 1st gear to the left and down with reverse directly above it. There are various names for this shift pattern- Getrag, dogleg, etc. This specific unit is also nicknamed the snailshell due to its physical resemblence. Officially it is the G31.
This turbo was ordered with the rare and coveted LSD option. The LSD holds a 930 part number and is 40% locking. Whether or not a stock 930 LSD is a direct fit is questionable as the G31 LSD part number is different by the last digit (often signifying a revision of the previous part in Porsche-dom).
If any 1980 931 owners want to check their box's for the LSD option, the serial number is stamped on the very bottom of the case (if you slide under the car on your back you'll be staring right at it). The font is small and the stamp is light and likely covered with lots of road grime (it took me forever to locate it), but the magic code the XXXX XXXXX /12. The /12 is the identifier. OR, you can look on your option code sticker for 220. Unfortunately my sticker is MIA for some reason.
Were it not for the LSD I would have replaced this box with a 944 Audi based transmission. This is only because the syncros in the Porsche box are notoriously weak, and this one was no exception. After opening it up I found the 1st and 2nd gear syncro hubs (aka dogteeth) were worn down to nubs rather than the pointy gears they once were. The pic to the left shows the worn 2nd gear dogteeth. This sort of wear can result in the tranny popping out of gear under acceleration. Lucky for me these hubs can't be gotten new either! -unless you pay Porsche for an entire new gearset, starting at around $1000+. So I called every Porsche transaxle shop in North America and some of Europe...
Powerhaus II was able to unearth a used 2nd gear hub in excellent condition (see pic to the right). Where they found it is anyone's guess! I quickly snatched it up. As of now I still haven't located a 1st gear hub and the transaxle is going to be reassembled shortly. The previous owner reported not having much trouble with 1st so I'm going to cross my fingers until I force myself to buy that replacement 1st gearset.
Along with the 2nd gear hub, I have replaced the 1-2-3 syncro rings. This pic shows the worn & new 2nd gear syncros. The new one has a very rough texture so that it grabs the gearset to set it in motion as you select the gear.
PowerHausII came through again. This time with a new 1st gear dogring. According to them, this is "the last one on Earth"! You can see how nasty the original dogteeth are compared to the new ring sitting above it.
While everything was pulled apart I replaced the pivot bushing atop the torque tube (which fits on the little ball nub on the end in this pic) and the rubber bushing on the shifter coupler. These changes and a healthy dose of synthetic 75w90 gear oil from Redline should result in some nice shifting. Just for grins, I replaced the old worn out shift boot with a new black leather piece. Makes a nice change!
So how does it feel? Shifting is very tight. You certainly know that you're shifting a 25 year old Porsche when you change gears. 1st gear is pretty sensitive. Shifts into first must be slow and deliberate and take place with the car either at a dead stop or very close to it. The worn 1st gear dogteeth cause 1st to pop out of gear on deceleration. Not too big a deal. The remedy is just to either hold it in gear with my hand on the shifter, or to simply let the clutch in if I'm decelerating in 1st.
2nd - 5th feel great and very tight. Quick shifts from 1st to 2nd at high (5000+) RPM will give a slight grind. 3rd-5th upshift and downshift smoothly at all RPM. It definately takes some getting used to!
