Shake in the rear of the car

[1985olds]

Good evening,



So, over the winter I did a lot of work to my 85 cutlass. New ls3, new McLeod rst, new quick performance 9”, new poly body mounts, new 2” lowering springs on all corners, new bilsteins on all corners, new frame braces, new front lca’s, new driveshaft. I have been chasing a shake in the rear of the car now since I got it back together. So far I have verified pinion angles, balanced the back wheels, verified the wheel base, adjusted my sway bar to not hit the rear end housing, moved my tailpipes to not hit the rear and verified not contact to the frame or anywhere on the axle housing. I still have a shake in the car. At 60 mph I can start to hear a groaning and by 75 it’s shaking. If I left off the gas at 75 mph it gets worse. Any ideas? Thank you.

[1985olds]

So the shake was the driveshaft. New pst 3.5” shaft and now it’s smooth again. I still have the noise though. I’m wondering if it’s normal for a Ford 9” or tire noise. They are cooper zeon Rs3-g1’s. Any thoughts?

[Hotwire]

I'm running the zeons and don't have any noise associated to them. Check your fluid level in the rear? Could be running too much aerating the fluid.