this summer i have noticed i have a vibration in my camino. if i have my foot on the gas to accelerate or for maintaining speed, the ride is smooth as silk. when i let my foot off the gas and coast i feel a slight vibration (osillation). i don't feel it in the steering wheel. i feel it in my butt.

new front end rebuild 2 years ago (plus alignment). new tires last year (plus balance). tracks perfectly straight down the road. more noticeable at higher speeds...45-50mph.

any ideas?

It's very likely a worn u-joint in the driveshaft. An easy way to check, which will only show if the joint is truly sloppy, is to jack up the rear end, slide under the car (safely please....) and try to move the joint from side to side on the center cross. Replace both joints if you aren't sure of their time in service.

Also, check out the transmission yoke for side excess side clearance (moving it up/down & side/side)- the bushing in the tail housing could be worn and need replaced.

I had something similiar years ago. It turned out to be the pinion nut on the rear diff was loose. Under power smooth but when you backed off and coasted in vibrated like heck

Is it a bad vibration or just a slight one? Does it do it at a certain speed? Or any speed?

thanks guys.

its not that bad. the rearview mirror does not vibrate or anything like that. but i can feel it in my butt especially on smooth roads. i'll drive it tomorrow and see it i can pinpoint a speed range where it happens.

thanks - oaw

I seam to have the same vibration you describe. Been hunting it for a while now.
Only difference is mine is at all times, during coasting also). I pulled the axles and found one very worn. I am hopeing that is the source of my vibration. You might want to check to see if you have any play in your axle shafts.