The car is an '88 Firebird listed in the sig. I've noticed a knocking from the rear (sounds like the passenger side) when the car is going about 20mph or so. It quits once you get going 30+. The previous owner said it had been doing it as long as he had it, and never though much of it. Also, when the tires lose traction the right rear wheel shakes violently. I don't know if the tire could be out of balance or what, but it doesn't seem right to me. I mean it shakes the car so hard, speaker panels and stuff start popping off.

Any ideas? I changed the diff fluid as soon as I got the car and everything looked ok, so I don't *think* it's the rear end. However, that change was the first change the rear had ever had - at 141k miles. Also thought I'd add the rear is an open diff w/ 2.73's, no other problems noted. Rides nice & quiet at 70.

 

Does it sound like it knocks once per wheel revolution? Or is it when it goes over bumps or something?

If it's once per revolution, it's either the axle and bearing, or something about the brakes.

 

Yeah, once per revolution but only at certain speeds. Could the axle and bearing cause the wheel spin shake too? I would think if it were the axle it would cause vibrations or noise on the highway, but I could be wrong.

Oh yeah, and the brakes SUCK. Pedal goes all the way to the floor before it will do anything. I just figured the brakes needed bleeding, new pads, etc.

 

Also, when the tires lose traction the right rear wheel shakes violently. I don't know if the tire could be out of balance or what, but it doesn't seem right to me. I mean it shakes the car so hard, speaker panels and stuff start popping off.

That's wheel hop. Do some searches on it. As for the other noise, it could be a number of different things(most anything that is spinning) Could be the result of the wheel hop--it can be bad on stuff.

 

I know what wheel hop is, but I guess I wasn't thinking that since it's an open diff, then only one wheel would spin/hop. I still can't believe that these cars wheelhop this bad stock. Something has to be broken.