I was at autocross lest weekend and noticed a severe lack of traction. My friends said I did a “one wheel peal” coming out of a few corners. Other than that, it works great in a strait line.

My car has about 80k on it and I have raced it at about 6 autocross events. It is stock except for an LS1 drive shaft and an exhaust cutout.

I have a few questions:
1. How hard is it to swap in a new LSD carrier? Will I have to get the gears reset?
2. Can my current LSD be rebuilt? What would be involved in doing that?
3. Is there any way to test an LSD to see how much bias strength it has?
4. Is there anything else I can go to fix this?

Thanks,
-Jason

 

I'm pretty sure that the LT1's came with the Auburn rear, as did my 98 LS1 (the only year for the LS1). Assuming that this is true, these units (I'm told) are not serviceable because they are cone-based rather than clutch-based.

I had the same behavior for the first time in my car at an autocross last Sunday. My short-term fix was to put in some Red Line 75W90NS gear oil. On my old 88 IROC with the Borg-Warner 9-Bolt, this improved the operation of the posi to the point that I didn't have to do anything to it... I am hoping that this magic in a bottle does the trick again for this car.

My first autocross should be this weekend with the Red Line Oil. We'll see if it is the "liquid locker" in my rear like it was in my old 9-bolt...

 

With the tranny in neutral, jack one rear wheel just off the ground. Block the other rear wheel against front and rearward movement. Tighten a lug nut on the raised wheel with a torque wrench aligned as closely as possible to a radial line from the center of the axle (with the wrench not crossing over the axle center). This will give you some idea. If the wheel starts turning at a reading of 15 ft-lbs or less, your diff is well on the way toward being un-posi. 50 would probably be OK, and I doubt that your OE diff would be set up as stiff as Auburn's 7.5"/7.625" Pro Series (~100 ft-lb IIRC). If you need a more accurate number, multiply the wrench reading by the ratio:

([torque arm length] + 2.375) / [torque arm length]

Note that this does not tell the whole story - after all, it's only one data point on the plot.

Norm

 

I read this over and over again but I just don't get it. If I turn one wheel with the car in neutral, it's just gonna spin the transmisson.

 

Not if there's anything left of the posi preload. Don't forget that you're leaving the other rear wheel on the ground (so it won't spin) and blocking it (so it won't roll). If you have an open rear or your posi is completely DOA, then one wheel and the d/s will spin without developing much of any resistance, maybe a couple of ft-lbs or so.

Realize that a posi wants to keep both rear wheels locked to each other until the bias (or preload) is overcome. Then, yes, one wheel, its axle, all the gears in the diff except the side gear for the other axle, the driveshaft, and the output shaft of the tranny will spin. That's why you put it in neutral, so you won't be including the torque it would take to turn the engine over against compression in your measurement. What you then read on the torque wrench as the raised wheel starts to spin indicates the amount of bias that is in the posi unit.

Norm

 

I replaced the Auburn on my 1994 Z28M6 2 years ago with a SLP HD torsen (unit used on the original Camaro SS, not the lighter duty torsen used after GM took over). Much better control than the Auburn. It can be fine-tuned with different weight oils.

From what I have read, I would have paid a couple more bucks to have the clutch pack Torsen T2R, to maintain forward traction if the inside rear wheel lifts, but I will keep this one for awhile.

Rick R

 

I WISH I could get a T2R....

 

Your stock Auburn has went south. SLP might have some takeout T2's for sale, or if a T2R is in the budget, you will never regret it (or replace it).