Crazy shaking

[cincy86]

I drive a 1986 MC sport coupe, 4.3, th350. When I drive at low speeds, it feels like I'm driving over small bumps, but when I go past 45, it shakes so bad that I don't want to drive it anymore. I have put the car up on jack stands and put it in gear, and when the rear wheels turn, they seem to roll out of round. Driveshaft spins straight, u joints are all good. I have replaced upper ball joints, all motor and trans mounts, harmonic balancer, and it does this with any set of wheels on it. Please help, I'm at my wits end here.

 

[pontiacgp]

sound like you have a bent axle...or 2

 

[pagrunt]

Maybe bent wheels.

 

[cincy86]

I had a bent shaft over the summer, and replaced it with a good one. both wheels rolled straight and true after that but not lately. I'm trying to get my hands on a ss parts car, I'm probably taking the rear from it.

 

[cincy86]

it does it with any wheels I have on it

 

[pontiacgp]

"when the rear wheels turn, they seem to roll out of round."

That happens with a bent axle. I had an axle that was leaking due to a groove so I changed it at the shop. The axle that was given to me by one of the guys at the shop was bent and I realized that on the way home. They had made a mistake and gave me the which came from a derby car..the car shaked real good on the way home but at least they had a good laugh when I changed the axle the next night

 

[Texas82GP]

Put it on stands. Pull the wheels and brake drums and turn the axles and watch the axle flange for runout, or check it with a dial indicator.

Any incidents related to this issue? How old are the tires? If you rotate the tires to the front, does the problem move to the front?

Just some ideas.

 

[cincy86]

It seems like it probably is the axle shaft(s), I just don't know what would have caused it to bend

 

[pontiacgp]

It seems like it probably is the axle shaft(s), I just don't know what would have caused it to bend

I have seen axles with a fatigue crack on the wheel side just past where the axle rests on the wheel bearing. We had a few break due to the force on the right rear in our circle track G body and F body. If I were you I would not drive the car until you pull the axle to check it out

 

[cincy86]

thanks, I think it will probably sit until I find a posi for it