xny1989

iTrader: (1)

I have a 99 camaro z28 m6, asr. For several months now I thought I had a bad rear tire, as I was having a low thumping sound coming from the rear of the car that would increase in frequency with the speed of the car. I never saw any bubbles in the tire or anything that looked out of round. To confirm it was the tire, I lifted the car off the ground today, put it in gear, and the sound continued. I removed the wheel and did the same thing, and the sound continued. I alos noted that the passenger wheel was now spinning faster than the driver side, since it has a lower load - it was making a kind of metalic thmping sound now. I removed the caliper and rotor, and the sound continued.
It seems to only come from the passenger side. I put my hand on the axle tube while this was happening and felt a vibration at the same speed as the thumping sound.

I've got an extended warranty on the car, so I'm bringing it in to the dealer, but wanted to get some thoughts on what this might be. A bad gear, bearing?

2MuchRiceMakesMeSick

I have never heard of thumping comming from a 10 bolt. I would look all around especially around the drive shaft area.

xny1989

iTrader: (1)

Y'know, I had thought that maybe the u-joint might be involved. Had a car that had vibration in the rear, turned out to be a bad u-joint - it would only pivot on one plane. Will check when the rain stops.
thanks

2MuchRiceMakesMeSick

Let us know how it turns out. I would like to know what causes a thumping sound. Who knows you might even help someone else out that has the same problem one day.

xny1989

iTrader: (1)

Well, I did a little more investigating yesterday and found that the u-joints are tight. I did notice some play in the rear though - I was able to turn the driveshaft about 1/8 turn before the wheels turned. Don't know if that is a problem or not. I then ran the car while it was in the air again to see if I could "feel" where the thumping was coming from, and lo and behold, it's coming from the outer edge of the axle tube, on the passenger side. It also seems that there is a tiny bit of wobble in the wheel when it turning, almost as if the axle shaft is bent. It wobbles at the same frequency as the thumping - so, it looks like I may have a bad axle and maybe a bad bearing as well. Although I've changed a seal in an old chevelle c-clip 12 bolt (1965) once, would I need any special tools to get the bearing out? Is the stock rear on a 99 z28 a c-clip?

Thanks

ex-SS-ve

iTrader: (9)

had that problem with my 3.42 rearend not too long ago. the thumping. ended up being a bad bearing on the posi unit.had the rear end completely rebuilt with new bearings. well a year later now the bearings are howling.. my luck. i guess i just got a crap 10 bolt.

xny1989

iTrader: (1)

Turned out to be bad bearings and axle's on both sides

1BADBLACKBIRD

iTrader: (2)

Resurecting this thread from the dead..I have an 02 TA. When it had only about 12-15k miles on it...It was making the eact same thumping from the drivers side. At that time every bearing in the entire differential except for the passenger axle bearing was replaced along with a 3.73 gear. Nothing was said to be wrong with any of the bearings upon removal. Now the car has 35k and it started the sound again. It went from what I would call normal to a very distinct thumping in less than 30 miles. I let the dealership do the last bit under warranty...even though I paid for all parts up front....this time I'll be doing it my self.....especially cuz the 3 year 36 month fell off about 2 days ago. Those bastards.!!!!!!!

99M6Z28

iTrader: (8)

I just repaired my thumping sound last night. I had to buy 2 new axles because both axle bearings went out and ate the **** out of the axles. So just replaced the axles with Mosers so they are a little harder now!