Transaxle went boom

Hello everyone!

It's been a long time since I posted here, but I couldn't have finished my conversion if it wasn't for you guys. I actually didn't post any pictures or anything since I "finished" so I put a couple in this post. (You probably have to look at the picture outside of the post because the they get cut off in the forum and I don't know how to fix that)

I think I need a new box. I could get a used turbo transaxle for about $500 used, or I could get a snail shell for about $1500?? I would like to do that, what is involved with the swap? It sounds like they were only available on the 924 turbo during the 1980 year. I thought someone on here had one? Any thoughts?

A lady took a left turn as if I I didn't exist at an intersection and I had to punch it to keep my rear end from becoming munched, as a result my transaxle destroyed itself. Every gear feels horribly crunchy and it makes a horrible racket in reverse. It doesn't go into gear easily at all. I haven't really investigated as this was on the way to work and I haven't driven home yet, but it felt really bad. It must have been on the verge of going for quite a while because I've been autocrossing it and generally not babying it without any trouble. Although I don't abuse it, I've never really done a burn out on dry pavement or anything.

I have 295's on the rear, I added the reinforcement plate between the castings, it has a solid mount and a brace to keep it from eating CV shafts.

Cheers,

Luke

my trans did the same thing on Friday...i've been looking at options for replacing it. I'm considering dropping big bucks on a turbo S trans, but this is the 4th trans I've had in this car, granted the first had 210,000 miles and was an N/A, the second still lives, the third was DOA when i bought it, and the fourth was a very nice 87 turbo trans with great syncro's, that lasted about 6,000 miles before it went bang in a similar fashion to yours.

I'm thinking that i may be blowing differentials, perhaps you did the same...i'm considering getting a LSD turbo trans, as I've read that the limited slip differentials are stronger than the open diffs, and don't suffer from the same problems of jumping under wheelspin and breaking. I'd love to know more about the snailshell trans swap, how difficult it is, what's needed etc.

http://garage.ideola.com/downloads/G31-Transaxles-PeteTinucci.pdf

just came across this in my searches...answers a lot of questions. The Snail Shell is a lot stronger, but requires you to swap torque tubes and all that fun stuff, so it may be more trouble than it's worth.

How many foot pounds of torque are you guys feeding these trans?
They were never designed to handle the kind of grunt that a big V8 can produce!

My box was rebuilt in '08 because I cooked the case of the original one. Now run a dif pump and cooler (track use only) My box came with a Quaife TBD which, based on the paperwork that came with the car, has been raced for over 12 years. When the box was rebuilt the Quaife we measured the parts and they were almost at original specs. So if you want to help your box get a Quaife. They are guaranteed for the life of the original purchaser and they do not void the warranty for racing!!

Find someone who has a proven track record for rebuilding 944 transmissions. They are not easy to rebuild properly. I have 90 track days on the tranny and it's not showing any signs of distress. One day averages 2 hours on the track. I run Swepco which is changed before the beginning of each season. I am running 295/18s on the rear and regularly hit speeds of 140+ at the tracks that I frequent.

Clutch dumping will kill these boxes as they were not designed for that kind of abuse. Experts say that a Turbo S box will hold 500 hp before really bad things start happening.

Torque is 355ft/lb @ 4100 & HP is 360 @ 6200

Marc

Good info. I had a turbo box from a 1986, which I heard was pretty rugged. Although I only had the open differential, maybe that was part of my problem. I added the reinforcement plate between the cast iron case at the end and the aluminum case, which supposedly reduces the risk of the casing flexing too much. I don't think that was my problem anyway. Maybe the solid mount had something to do with it.

Marc, is the Turbo S transmission any different than the standard turbo box? Asides from coming standard with a limited slip probably? Do you know anyone who is running the "snail shell" from a 931, I've heard really good things about those. Alternatively I could get my current unit rebuilt, what shop did yours?

I was actually looking at the wavetrac differentials, they would be capable of 100% lock. The Quaife TBD's still behave like an open diff if one wheel parts company with the ground completely I believe.

Thanks for the link to that paper, I'll read it this weekend!

Luke714 wrote:Good info. I had a turbo box from a 1986, which I heard was pretty rugged. Although I only had the open differential, maybe that was part of my problem. I added the reinforcement plate between the cast iron case at the end and the aluminum case, which supposedly reduces the risk of the casing flexing too much. I don't think that was my problem anyway. Maybe the solid mount had something to do with it.

I do not have the reinforcement plate. I do know that solid mounts are NOT recommended for 944 trannys. Most racers are filling the OE unit with urethane (which can be purchased from McMaster-Carr) so that they are more rigid than the rubber, but absorb enough vibration so as not to create a problem.

Luke714 wrote:Marc, is the Turbo S transmission any different than the standard turbo box? Asides from coming standard with a limited slip probably? Do you know anyone who is running the "snail shell" from a 931, I've heard really good things about those. Alternatively I could get my current unit rebuilt, what shop did yours?

I believe, but not certain, that some internal parts of the S box are hardened. My feeble memory says someone on this board is running the snail shell. Charlie Murphy rebuilt my box. He is an owner of Intersport in McLean, Virginia.

Luke714 wrote:I was actually looking at the wavetrac differentials, they would be capable of 100% lock. The Quaife TBD's still behave like an open diff if one wheel parts company with the ground completely I believe.

Not sure, just know that I don't have any traction issues unless I over accelerate coming out of a turn, then both wheels spin

I do know that solid mounts are NOT recommended for 944 trannys.

Could you post a source? I searched rennlist and couldn't find anything on this.

actually, are you referring to this?
http://forums.rennlist.com/rennforums/944-turbo-and-turbo-s-forum/436557-solid-transmission-mount.html