Hey all, the rear end of my '91 740 sedan is shaking from side to side upon braking or acceleration between 10-25 mph. I have checked the bearings, rims, weights, tires, and drive shaft. The only things that my father can think of is that a brake pad is sticking on one or both sides or a disc brake is warped. The discs seem straight. Any ideas?

 

sure one of the rims isn't bent? I think I'd jack up the rear and with the car in neutral, spin each rear wheel, using a pencil or something held against a stationary stand as a guide to see if there's more than a MM or so of side to side motion at the permieter of the rim as the wheel turns

bad panhard rod bushings would make any side to side motion much worse, so I'd check those (thats the transverse rod that goes from one side of the rear axle to the frame on the other side). with the car on the ground, if you push the back side to side, do you hear or feel any clunking?

 

Adding to what Pierce mentions...the simplest thing is bent rims or a broken belt in a tire. So...if an issue isn't obvious, swap the tires front to back and drive it. If the sensation changes or goes away, you've found your culprit.

 

bent rims can really trash your suspension too. your ball joints and bushings are getting hammered at wheel rotational speed.

 

I have check the rims, and they are not bent or warped.