I need some help with a problem I'm encountering which my local dealer, or GM, has not been able to solve.

Here's the situation. The positraction clutches seem to be seizing when the steering is close to full lock, either direction, and whether backing up or going foward. This generally occurs when the car is started first thing in the morning and the weather is cold. It also occurs even if the car has been driven that day, but when it has been sitting, during cold weather, long enough to cool down.

Following a GM service bulleting, the dealer has drained the rear end and replaced the oil and anti-seize compound twice, with driving 1000 miles between each change, per the service bulletin. When this didn't solve the problem, a new clutch/disk pack was installed. Now that the weather is cooling off, and with only 2000 miles since the clutch/disk pack was replaced, I am still getting the positraction seizing problem.

Any advice would be appreciated. The dealer, and GM, have pretty much thrown their hands up and say they've done everthing the can per the service bulletin.

Thanks,
Dale Yellin

 

Have you checked for a cracked diff housing/case?

 

My mother's '99 had the issue and I simply added a bottle of the limited slip additive which is what I assume you mean by "anti-seize". I went out and did some figure 8's in the culdesac and it was fixed.

Oddly, this past Saturday my father called me and said he thought his '04 Z16 Z06's diff was broken... he described the same symptoms... chattering/grinding clutch backs in low speed sharp turns.

Told him what to do and 30 min later he called be back to let me know it was all fixed.

Stupid question, but are you sure GM is putting the necessary amount of additive in?

Also, try getting another bottle of it and fill it up... it may work. The GM tech who used to do all my warranty work told me he'd always put 2 bottles of the additive in because 1 didn't always fix it and he'd get repeat customers because of it. One he started using 2 nobody ever came back for remaining noise.

And don't worry aout draining the dif, or draining a little out. If it's slightly overfilled that's ok, there's a weep hole at the top of the diff that will vent if excess pressure builds up.

HTH,
Brian

 

My car does the same thing. I changed fluid and put in the additive. No change....... It's kinda normal, the rear end locks up nice and tight with almost no slippage. Its just the nature of a high performance differential. But I do agree, it seems more noticeable in cold weather.

 

It is pretty easy to do a fluid change yourself. I would try another fluid for the rear, some have the additive already mixed. Or you could add more slip additive. Keep us posted.

 

When I got my 03-z in May of this year it had 5250 or so miles, had all fluids changed at a good repair shop.. It started makeing the same noise, took it to the dealer they change the fluid and added the additive (not sure how many bottles) have had no problems since.... Not one sound...

 

Thanks for the suggestions. I shared them with the dealer this afternoon. As a result, they've agreed to re-service the rear end, per the new service bulletin, with Mobil 1 and two bottles of GM Positraction Fluid.

I'll let you know how it is working in a couple of weeks.

Dale

 

That's exactly why I am not changing any fluids.

 

How many years or miles are you going to but on your car before you do change any ????

 

After the dealer services the rear end, see if they do circles in both directions (4 or 5) of figure eights as Cobra4B suggested. You have to get the new oil and additive in between the clutch disks. I have been serviceing vette for 18 years. I always do this.