rearend growling

[davidkouns]

Hey I'm new to the site I just bought a 99 trans am the rearend growls all the time and it feels like the back of the car is bouncing up and down do you all thing this is a internal problem or possibly brakes and tires it has sat for over a year

[sjgreen6]

Davey,

Welcome to the site. The rear end is definitely subject to abuse and damage on these cars. It would help if you can tell us a bit more about your car (auto or manual transmission, miles, suspension and engine modifications, etc.) as sometimes one thing can affect other things. First step would be to get your car up in the air and inspect your suspension to ensure something isn't loose and causing your problems. Next would be to take a look inside of the rear differential. Probably needs to have the fluid replaced anyway. If you see anything that looks like metal shavings, filings, or other damage you will want to consider rebuilding, replacing with a used unit, or upgrading to a stronger axle. Many will tell you that rebuilding is a futile waste of money, replacing with a used unit may be cheapest but may also be hard to get exactly what you need and it may turn out to be in poor condition as well. If you don't find damage in the rear, be sure to refill with the limited slip additive from GM in addition to the gear oil.

Check the other forums for many, many, many threads about rear end problems and solutions.

Steve

[35th-ANV-SS]

Bouncing up and down could also be related to shocks and/or springs. Steve has suggested some good ideas. Let us know what you find.

[theorangeguy]

I'm going to go out on a limb and bet that your car still has the stock springs and shocks and the bouncing is probably coming from the shocks being worn out which means the springs are free to do what they want which will certainly cause the rear of the car to be springy.

[2002ssslp]

Welcome to the site Davey. You are going to learn a lot from the members on this site.

[davidkouns]

Davey,

Welcome to the site. The rear end is definitely subject to abuse and damage on these cars. It would help if you can tell us a bit more about your car (auto or manual transmission, miles, suspension and engine modifications, etc.) as sometimes one thing can affect other things. First step would be to get your car up in the air and inspect your suspension to ensure something isn't loose and causing your problems. Next would be to take a look inside of the rear differential. Probably needs to have the fluid replaced anyway. If you see anything that looks like metal shavings, filings, or other damage you will want to consider rebuilding, replacing with a used unit, or upgrading to a stronger axle. Many will tell you that rebuilding is a futile waste of money, replacing with a used unit may be cheapest but may also be hard to get exactly what you need and it may turn out to be in poor condition as well. If you don't find damage in the rear, be sure to refill with the limited slip additive from GM in addition to the gear oil.

Check the other forums for many, many, many threads about rear end problems and solutions.

Steve

It's a automatic transmission with 170000 miles and the it's all stock. I'm working 7 days a week right now I don't have any time to work on it so it'll be parked for a few weeks until I get time to inspect everything thanks for your reply

[sjgreen6]

It's a automatic transmission with 170000 miles and the it's all stock. I'm working 7 days a week right now I don't have any time to work on it so it'll be parked for a few weeks until I get time to inspect everything thanks for your reply

Given your high mileage there are a lot of suspension components that if original are definitely suspect including the shocks, springs, and suspension bushings. If everything looks stock then it is time to inspect everything carefully and look at replacement parts as needed. If there are aftermarket parts, definitely look at all of the mounting hardware. All of the suspension components have specific torque requirements and the bolts should be torqued while the suspension is loaded in normal riding position (not hanging suspended from jack stands). When the parts are worn or installed incorrectly they can definitely cause some of the problems you described.

The automatic cars tend to be a bit easier on the rears but you never really know how the car was driven by previous owners. Your rear end growling could be damage from wear and abuse or could be as simple as someone changed the fluid but did not add the limited slip additive. Yes most bottles of gear oil will say they are for limited slip applications but these GM rears tend to make a little noise if they don't get the additive. Easiest place to find it is on the internet or at any GM dealer. You need a 4 ounce bottle of GM Part number 1052358 added to the axle along with a fill of gear oil. Again, look for signs that something has been changed in the rear end. Aftermarket covers, bolts, changes to rear gear ratios are all tip offs that someone may have made a change to the original rear set up that is the source of your problem. Changing gear ratios and getting everything set up correctly to ensure long life and quiet operation is a black art that can only be practiced by a mechanic of superior skill and patience.

Good luck!

[sjgreen6]

Something else to consider is that you could have a bad axle bearing rather than a bad rear. While the car is up in the air see can spin the wheels with the trans in neutral and listen for noise coming from near the wheels rather than toward the center of the unit.

[02ragtop t/a]

Hi. I had to replace the axle bearings on my '02 WS6 6/m at 28K miles. That was in 2007. No warranty. The shop that did the job said that the bearings should NOT have self destructed like that at that low mileage. When I sold the car in 2012, the rear was growling and grinding again with only 58K on it. In my opinion, if your bearings are shot, you are better off replacing the rear with a 12 bolt or 9 -inch from the aftermarket.