DatBassTho

Looking for my first 951 and doing my research. If I were looking do to a total drivetrain overhaul for more reliability and slight boost in power (~300hp), where would you begin? I dont dont care about keeping it stock or original to the car. Maintaining the value of the car or originality of the mechanics is not my goal.

Thanks!!!!

MAGK944

V2Rocket

figure $500-1000 for a rebuilt torque tube, and $1500-$3000 for a rebuilt transmission, depending who you use.

the stock parts are up to the task of 300hp but should really be freshened simply due to age and mileage.

odonnell

For the reliability and power, I would look into a standalone ECU + electronic boost control.

DatBassTho

From engine to the rear axle. Thanks!!! I'll look into these. I'd like to to make a bit more power than stock, nothing crazy but I'm well aware, the stronger the foundation the easier it is in the future to maintain.

DatBassTho

That's doable. Is it recommended to go with a stock trans or is there a way to beef it up and make a stronger core than can handle more? Or is there even a different trans altogether that is better?

DatBassTho

Have any suggestions on a standalone ECU?

bumflick

VEMS

Check out pnpecu.com

Otto Mechanic

I used the stock S2 gearbox (AOR I believe), added a transmission cooler and stock ZF LSD. I have similar HP goals and from what I understand this is the strongest stock box available, with the possible exception of the 6 speed 968 box. I also decided on the "short" 5th gear since it's a track car and I don't anticipate needing the car's top speed often.

PS: I also highly recommend the Only944 short shift kit and solid transmission mounts.

DatBassTho

*Deleted*

DatBassTho

What can the stock S2 gearbox handle up to? Mine will primarily be a road car that will be on the track every so often. I just really want to solidify the entire drive line so I can set it and forget it. Also, do you have links to the cooler and LSD you used? Did you put them in yourself or let a shop do it.

Thanks,
Jordan

Constantine

The stock 994T, 944S2 and 968 transmissions will handle past 300HP/TQ figures, however a lot is in how you drive it and how much track time you will see with it.

We have clients who use these stock transmissions in V8 conversions and they do quite well with them.

Anything you can do to help the transmission/differential stay cooler and help with its internal lubrication (using proper lubricants) will extend its life span. Hard track use, missed grinding shifts and hot temperatures will shorten its life.

As far as torque tube internals, one of the biggest problems is skimping on the rebuild and using drive shafts which are damaged or are worn out at the pilot bearing end nub. Torque tube and drive shaft problems will damage clutches and sideline a Porsche, no matter how much money was spent on an engine and transmission rebuild.

Also try to stay away from split torque tubes found in all 944S2 and early 968 Porsches. The split torque tube will give you problems which are not easily fixed until you change the split tube for a non-split tube. Non-split 968 tubes are very hard to find.

Good luck with your hunt.

DatBassTho

Good to hear on the trans. I definitely want to get the cool as possible so a cooler will most likely happen when it is time. I'm already planning for a full 4 bearing (I believe that is their highest offering for ~$700) torque tube rebuild and or new TT from black sea. I'm also gonna just go ahead and get it powder coated. I've read some horror stories on the split tubes and will definitely pass on that! If I can I'd like to go for a 88 951 Turbo S if it's the right condition that I'm looking for. Now on to the LSD and rear axle and trying to understand what works and doesn't and best route to go.

Otto Mechanic

I've never seen published engineering numbers for torque or HP on any of the gearboxes, I've just read stories and experiences coming from folks who've built high performance racing motors for our cars. Most of what I've read comes from threads on this site, I'd suggest starting by reading the stories and build threads posted on the 3 liter Turbo Registry thread. Most seem to agree the AOR transaxle (actually built by Audi) is the over all strongest box and recommend hardening the 1st and 2nd gears (or transplanting them from a 951 box) for high output motors. Kevin Gross (Catellus Engineering) specializes in building racing transaxles for our cars and if anyone might know the "official" numbers for the various transaxles that have appeared on them over the years, it would probably be him. You can find him posting occasionally on this site and he helped me a couple of times when I was re-building my box a few years ago. If I'd lived near him I'd have taken my box there for the rebuild but I'm on the west coast so ended up using an Audi transaxle specialist in Santa Clara CA who did a very professional job in my experience (at least so far, with less than 500 miles on the box. Keep fingers crossed

I found a rebuilt ZF LSD (original equipment) and stock trans. oil cooler through a fellow named Dimi Paralanov who owns FlyingHorseMotorsports.com back east. He was very helpful setting me up with all the parts I needed to rebuild the AOR on my S2 and he should be able to help you out if you're trying to stay stock, which I was. You'll likely hear good things about more contemporary aftermarket LSDs for our cars, the Guard seems to get a lot of respect along with the Quaife. I'm trying to reproduce one of the "Super 7" cars of early 90's Firestone Firehawk fame so I didn't consider those options.

I did bend the rules a bit with Constantine's Super Bearings during the TT rebuild, excusable in my opinion because the stock TT bearings are NLA and I wasn't convinced rebuilding the old ones was a reliable choice. At his advice I also replaced my "split" TT with a solid tube I salvaged from an older car. I just blasted and painted mine rather than powder coating it.

I used a SPEC Stage 3+ clutch and I'm happy with it. Its not deep and it takes getting used to, but that's the way it's supposed to be. I'm still using stock CV joints and axles but I did replace all the CVs with new (not remans, I don't trust them).

I also replaced all the bushings front to back and of course refreshed the rest of the suspension. I've yet to do anything to the motor, my plan is to put a couple seasons on it to get what I've done so far dialed in, then begin working on power.

Good luck on your journey,

GPA951s

I was going to say the "path" to Drivetrain rebuilding starts at the bank :-)

Seriously, 300hp Not an issue, just Drive a higher HP car with your head, Dont dump the clutch, power-shift it so hard it "shocks" the drivetrain... Ease into it, no matter what you have or get be smart with it and it will last a long time

Im on My 4th 944 turbo and still have three, NEVER had a driveline issue (18years and counting) and am running over 300 on all of em... Including the Racecar which has a Tec3 Standalone..