Need help figuring out wheel hop/shaking issue!

[GThomas]

Hey guys,

Issue : rear end (seems like both wheels) shake violently under hard acceleration in all gears. Makes a shudding noise but only under load.

Normal driving is good, but this happens on the gas in any gear, even in 5th if I punch it on the highway.

It is not effected by turning or bumps.

What I've checked and fixed:

Last week the CSB, Tranny mounts and diff mounts were changed, (e30 M3 CSB/ AKG Tranny Mounts, M coupe Diff mount)

The CSB and tranny mounts were pretty shot, after changing them all of the driveline noise was 90 % lost and we found the u-joint to visibly look okay when changing the CSB. But the shaking under acceleration was still there.

What I've tested.

Jacked up rear, both wheels don't seem to have any play at 6-12 9-3, the axles only slide in and out about an inch but nothing side to side. The wheels don't make "wheel Bearing" grinding when i spin them. I swapped two other wheels and tires on the rear and the issue still occurs. A friend driving next to me watched and said the rear wheels was shaking and hopping like nuts under hard acceleration

Here is what I can think of:

Axles
Wheel bearings
U-joint
Subframe mounts (PO did AKG Poly about 20K ago though)

ANY THOUGHTS???

[wodcutr]

blown shocks on the rear!

[GThomas]

blown shocks on the rear!

Yeah, had not really thought of that since the car has been handling okay for autocross and not making any different movements on bumps. I will have a look at them for sure though.

[Boris3]

I didn't see motor mounts in the replacement list above. If the tranny mounts were shot good chance the mm are also shot. Easy to tell when they shear but sometimes they may be gone and just not sheared yet.

[GThomas]

I didn't see motor mounts in the replacement list above. If the tranny mounts were shot good chance the mm are also shot. Easy to tell when they shear but sometimes they may be gone and just not sheared yet.

Motor mounts are AKG poly swap mounts with only 9k on them, so i doubt its them. and it is noticeably from the rear. The shock is still suspect but i had a friend drive next to me and he said the wheel hops side to side and not up and down.

[wodcutr]

Maybe your axle nut has backed off!