After getting the suspension sorted with the new Borla exhaust system, I went on a quick drive and found the rear axle was noisy, like marbles rolling inside a tin and the rear axle was wining louder the faster I drove.
When I put the car back up on stands and started testing things, I noticed a lot of noise on the drivers rear side of the axle. It really sounded like bearing noise, so I decided to replace the axle shafts and bearings to be on the safe side. The previous owner replaced the pinion bearing about 3 years before I owned it and there were no leaks. I assumed there should not be any other issues with the diff. Once I had the cover off, the oil was pretty much trash, though I didn’t find any major chucks or anything just typical gear wear and the gears looked evenly worn. I went ahead and replaced the axle shafts and bearings and added new seals, in the process I found the drivers side parking brake shoe was loose, you could easily grab it and shake it around. The lightbulb went off at this point, that the issue may not have been with the diff but with the parking brake. I got new shoes and brackets to hold them in and this time the new shoes were snugly installed. I refilled the diff with heavier oil and also added GM posi additive, even though some folks say not to add it for this style of rear axle, a Torsen, there was a service bulletin from GM in the 2000’s that recommended adding the posi fluid to fix noise issues, so I did it. I figure it cannot hurt.
Results
Driving the car with new diff fluid made an improvement, the wine at higher speeds was gone completely, but a new rattle like sound in the driveline is now apparent, a completely new sound, though quieter than the previous one. This sounds like a metal ring bucking back and forth or spinning around a shaft. I have not addressed it yet but further research it may be that the Torsen just makes this noise. It is only present when deaccelerating or letting off the gas at low speeds. It definitely has something to do with the thrust against the rear diff. My plan in the fall is to take the drive shaft out and take it to get new U joints to see if that solves the latest noise issue. If it doesn’t, I will wait until spring, change the diff oil again and reverify there is nothing bad going on inside. From what I read the Torsen diff’s are just noisy, and the 4th gen forums as well as ls1tech recommend replacing the rear axle with an aftermarket 9″ as the solution. I may just have to do that in 1-3 years if this noise doesn’t sort itself out.
The only other complaint is the car stance is slightly off, the rear feels a bit too low. Some weekend I will jack of the car and add a 1/2″ spacer to the spring upper rubber pads to lift the back a touch. A half inch will go a long way I think.
Next post will cover the Apple Carplay/Android Auto system with rear backup camera installed in this 2000 Trans Am, as well as back to projects for the 1981 Trans Am which includes a RetroSound Daytona M2 radio and New Vintage USA gauges. Stay tuned!