Vibration at 25 and 50 mph

695MPH

MEMBER
1925 CHEVROLET S-10

I have a 98 s-10 2WD 5sp manual 4cyl 115K miles ext cab. Vehicle shakes like crazy at 25mph and 50mph, independent of braking, engine speed, acceleration, or gear. Had tires balanced, no effect. By jacking only the R, and then L rear wheels off the ground independently, I duplicated vibration at wheel speed of 25pmh in both the lifted L and R wheel cases while car was sitting still. I heard no pronounced grinding when spinning tires by hand, noticed no visible wobble in wheel. Driveshaft on this model is 2pc, going through center bearing. Weight on rear driveshaft appears to be intact. No caked mud, visible cracks or dings in either driveshaft. All U-joints are solid. I dont know what to make of ~5degrees of freeplay in shaft (while in N) at (open) differential end. No leaks from dif or trans. Any suggestions?

1 Reply

SERVICE WRITER

MECHANIC
9,123 POSTS

Get a real good look at the center bearing. Tis is the source of vibration that I have seen the most on these.

Try jack the rear end up, supporting it with jack stands and then start it and put it in drive. That may reveal the source. If not gradually increase the rpms, my bet is it will show.