924Board.org

[newman931]

Hi:
How much torque can the rear end take on a 924 turbo?
what has to be done to increase this?
is it possible to build the tranny for higher gears?
thanks for input...

[ideola]

That depends on which year you're talking about. The 1979-1980 US spec 931 had the G31 (a.k.a. snailshell), which is regarded by some as the strongest gearbox available (in terms of torque handling capacity) for the 924-944 product line. The 1981-82 US Spec had the Audi based gearbox, while the ROW versions stayed with the G31.

The Audi box is no slouch, there are 944 guys putting out serious power on those boxes. But it's also no coincidence that the G31 was retained in the more powerful ROW 931s, and also the basis for the CGT and GTR gearboxes.

v8carreragts has an EXCELLENT writeup on the Porsche gearboxes which you should read. You can access decent resolution JPG images converted from a PDF here: http://picasaweb.google.com/streetlegalporsche/G31TransaxleInformation#
Or you can send him a PM and ask him to email you the PDF.

Interestingly, I was just at my trans rebuilder on Tuesday night looking at 3 different G31s I'm in the process of consolidating into two good units (hopefully). He was commenting how similar many of the features were to the G15, which was installed on 911s and 911Ts with more power than the 931. Then he pulled open a drawer full of 915 gearsets and was shocked at how much LARGER the G31 stuff was than the G15. Case is larger too, although the fore-to-aft length of the main gear housing is shorter by at least an inch or two. In any event, his comment was that the G31 must be VERY capable in terms of torque handling given its favorable comparison to the G15. The fact that it was used in the 375HP race version of the 931 is further evidence of Porsche's thinking on the matter.

{EDIT}
Forgot to directly answer your one question...according to Pete's document (linked above), he comments that it should be good for at least the 450 ft lb that the 915 gearbox was rated at by a couple of independent shops.
_________________
erstwhile owner of just about every 924 variant ever made

[newman931]

WOW!
Thanks Ideola!
I am new to this stuff however, I have been reading here and on 924.org for a LONG time. Tryin to make sense of all this. Sorry I didn't note - my 931 is 1982. So, I guess I wish I didn't have the audi tranny, huh?
From reading, it sounds like the gears are kinda low, is this true?

[ideola]

Gearing is sort of a personal preference, and depends on how you drive, and also how you intend to use the car (street vs. track). You can download Applebit's excellent spreadsheet showing all the various gearbox ratios here:
http://garage.ideola.com/downloads.html
First column, under the "More Tools" section, file entitled "Porsche Transaxle Gearing"

The Audi box is not a bad box by any stretch. It certainly has it's advantages...cheap, plentiful, strong enough, durable, etc. It was always available with LSD, but this option was very rare from what I've seen in the US S2 931. However, the later 944/951 LSD-equipped Audi gearbox will more or less bolt right in to an early chassis. The gearing might be a little tall for a 931, but it really depends on your use and driving habits. A lot of the racers like to take the short 5th from the 1987-88 924S and put it in their LSD-equipped trackable 944s & 951s. Certainly doable, but of course, incurs some labor expense to have the LSD swap or 5th gear swap performed by a competent and adequately equipped trans mechanic.

Tell us about your plans...how much torque are you hoping to produce?
_________________
erstwhile owner of just about every 924 variant ever made

[newman931]

OK, this might be kinda awesome!
I read Pete's write up on transaxles.
thanks ideola!!

alright ideola, I'm not sure what people on here would think of my plans for my car?! MANY will not appreciate it. in reading on these forums as a guest for a while, i've seen a lot of trash talkin' and stuff. i don't really want people doin that to me. but i'll tell you anyway.

What I love about this car and the reason I bought it was for the way it looks. I've always loved Porsche, so I got one. about 3 years ago. been in my garage ever since, while i try to decide what to do with it. i've had 2 different VW beetles, (73 and 74) fun cars. the doors on my car sound exactly the same as my bugs when they are shut. that's cool to me...

So, my plans:
I am converting it to a TDI. Reliable and VERY good gas mileage.
If I can find a 16 valve TDI motor (euro) I can push over 250 HP and still get about 60 mpg's. Even if I can't find the 16 valve, I can make just over 200 HP, which is about what a GT gets with the numbers matching.
The TDI brings crazy torque, it will be a fun car to drive!
So, to a purist this is probably sac-religious, but i don't care. I don't have the money to be a purist.

So, let the scorn begin...

[Rasta Monsta]

I have 951 LSD gearbox for sale you may wish you consider for your project. . .

And, IMO, there is nothing "unpure" about swapping one VW/Audi lump for a different one. . .
_________________
Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[newman931]

Thanks for stickin up for me Rasta!
I agree!
I'll keep the LSD in mind.

[ideola]

I agree with Rasta...I think it would be uber-cool to see a TDI-power 924!!! You've probably already spent time in the Engine Swap sub-forum here...but you may not be aware of the Porsche Hybrids forum, which will be very receptive and helpful to what you're contemplating.

Rasta's LSD box would be a nice piece for your setup...
_________________
erstwhile owner of just about every 924 variant ever made

[!tom]

[newman931]

Does anyone know if the gears from an Audi 5000 TD will fit into the 016 tranny??????

[ideola]

You know it's bad form to bring a thread back on topic once it's been de-railed, right?

Just kidding, of course! Sorry, I don't know, but try giving v8carreragts a PM, he's very knowledgeable on these gearboxes.

Free bump.
_________________
erstwhile owner of just about every 924 variant ever made

[newman931]

Sorry!
I'm bouncing between forums to try to make sense...
I was informed that the torque pre 2000 rpm would shred my gears.
If the audi 5000 diesel gears will fit in my gearbox - its a fix.

"In stock form the 016 will push the rear support bearing through the center section @ 300 ft/lbs of torque. The 5th gear will strip shortly thereafter. Many people with high horsepower 5 cylinders (500+) can shred teeth on gears 1-3 with a full throttle launch."

Is this a vendor trying to get work, or what????

[ideola]

Dude, what kind of power are you trying to produce out of the 931??? Or are you doing an engine swap? You are unlikely to strip gears in either the G31 or the 016 until you exceed 400 ft lb of torque, which you're very unlikely to produce on the 931, especially below 2000 RPM.
_________________
erstwhile owner of just about every 924 variant ever made

[newman931]

i am going to put the TDI under the hood.
i'm on a couple tdi forums all the time trying to find out how to make all this line up before buying stuff that won't work, and trying to figure out what will be BEST.
All these guys over there are saying i'm getting into way too much torque for my tranny and drive. yet - i can't find where their info is based from, guessing experience... don't know. but i haven't seen or heard of anybody actually getting the vw tdi in a 931 yet. i've seen the audi 2.5 TD in a 924, but not the VW TDI. i guess i'm too green at all this uncharted waters crap or something. i AM going to do it. i just don't want to break too much crap trying - my budget doesn't allow for much, if any of that.
i'm putting the 4 cyl tdi in it - not the 5 cyl. with a few mods i'll be at right aroud 200HP (that's about what the GT gets). not sure how that translates to torque in the diesel world.
i'm NOT tryin to break any salt-flat records or even take it to the track. the street is my track. i just want a QUICK, FAST, NIMBLE little car that gets 50+ mpg.
ya know?!?

[newman931]

oh yeah-
how much does a 951 gearbox w/LSD cost???
(rasta)
are we talking the whole transaxle? or what?