Hello all, I am hoping fellow third gen owners can help me because I am at my wits end. I have an '83 Trans Am with limited slip differential. When I make slow turns (like going through the drive thru at McCdonals') the differential will shimmy and shake like crazy. And as you drive it longer, it tends to get worse. A nasty clunking sound can also be heard. It is driving me insane as I have tried and tried to figure it out.

Tire balance...NO. Differential fluid change...No. U joint and drive line inspection....No. Rotated the tires...No. It's a great car and would run very well if it wasn't for this. I've read all about limited slips and how one wheel compensates for traction while the other is moving and yada yada yada. But somehow I don't think it was ever intended to shimmy from side to side like this.

If anyone has any ideas or has experienced anything like this, plaese post back. I need some help!

Scott

 

when you changed the oil did you put posi additive in it?

 

Ede's right. Make sure you have some limited slip additive. You didn't mention it, so that is what it probably is.

It sounds like what my car did when I got it from the previous owner. I put new lube in there that "supposedly" had limited slip addtive included but it still didn't fix it. Finally, I put the GM one in and that did.

 

It WAS limited slip additive guys. 80/90 grade synthetic limited slip differential fluid. I thought for sure that would cure it, but still nothing. I wonder if it could be the stabilizer bar? That's about the only thing left I can think of. My last resort will be to take it into Chevy or Pontiac and let them have a try.

 

before you let them have it, i'd pull the diff cover and have a peek. you may have broken something. then, when you put it back together, use syn oil, AND a limited slip additive. Mobil 1 says it's syn gear oil is "safe for use with posi and limited slip axles", but (IMO) i think they forgot to add "as long as you put limited slip additive in as well"

 

gear oil isn't posi additive. go to gm parts and get a bottle of posi additive.

 

Even if it does say that it has limited slip additive in the lube - do it anyways. I recommend you get the one from GM too. I've tried others to save a few $$ and they don't seem to work right. Even if they say they are GM Part #***** equivalent.

I know if the limited slip additive is not in there it sounds like there are very serious problems back there. It happens most when the axle is hot and when your doing something like turning in to park your car and not when your driving in a straight line. It seems like a few ounces of oil won't help. In this case it does. Well, at least it did for me. I'm almost willing to bet that it will solve your problem too!

 

Alrite JA, I'll give that a try. Heck, I've tried just about everything else! Now your saying to add strictly GM limited slip differential fluid right? And nothing else? Also, would I get this stuff at my local Pontiac or Chevy dealer you think?

 

Yes, usually the dealer will have a few bottles. Call the parts counter before you go to save a trip. If they don't have it there, ask them to check the network and tell you where you can get it.

It was like $9 for a little bottle the last time I got it.

 

K will do JA. Thanks for the advice. After I put it in and do a couple test runs, I'll post back and let you know. Thanks again


Scott

 

dude, before you run off and do something nuts, i think they're saying use gear oil... the 80-90 weight stuff like normal... but before you add in the gear oil, add in limited slip additive, the kind that you get from the dealer. the stuff you're gonnd pick up? it comes in a little bottle. you add that to the rear, and add your gear oil in after it, and then close it up and go run it. I'd recommend taking off your diff coer, to fully dump the old fluid out. then put it back on, seal it/bolt it. add your gm additive we told you to get first, then add the gear oil. that should stop the chattering, assuming you didn't see anything wrong when you popped the diff cover off. good luck, keep us updated.

 

GOOD NEWS!!!

I went out Pontiac after work today and picked up a bottle of the limited slip additive. I explained to the guy what was going on and he told me almost the exact samething as you guys did. As soon as I got home, I put the stuff in, went for a test drive and NO SHIMMY!! And I made sure I tested it very well....I made turn after turn and there wasn't a shim or a shake to be felt. After living with this for so long, it was like driving a new car altogether!

Can't thank you guys enough for steering me in the right direction. THANK YOU THANK YOU THANK YOU!!!

Scott

 

awesome. now stop screaming like you used that herbal shampoo on TV.













j/k


glad you fixed it.

 

Cool! We knew it!!!!

I remember when people told me about the limited slip additive, I thought they were nuts. I know its hard to believe until you actually see it work.

 

Indeed your right, JA, it is hard to believe until you actually see it for yourself. Amazing how that particular mixture from GM can work with those gears and solve everything. Almost doesn't seem possible but it is. Well thanks again for all your help. It's been much appreciated

Scott