vibration when coasting at highway speed

[basketcase]

My 90 v1500 sub has had a slight vibration when coasting since i got it in april 04, but last night i noticed that it is much worse. when i let off the gas at 65-70 mph i feel a vibration from the rear that feels like riding on the rumble strips on the shoulder! i am kind of thinking u joints, anything else that could do this? the truck has 4" blocks in the back 700r4 and 10 bolts(yuck).

 

[Leper]

If you put it in neutral, does the vibration stop?

 

[zeroz400]

Does it only happen at speeds around 65-70? It could just be a slightly out of balance tire. Check your u-joint, if it checks out fine then you need to shim your pinion up more.

 

[basketcase]

vibration coutinues in drive or neutral, it does still vibrate at lower speeds, but nowhere near as badly

 

[89K5guy]

Do you feel the vibration in the steering wheel or from the rear of the vehicle?
if it is coming from the front it could be wheel bearings or upper/lower ball joints.If the u-joints check out then it might be the pinion bearing
The only small item that wouldn't cost much to check would be to have the driveshaft rebalanced.Hope this helps a little.

 

[mikayak390]

My vote is a bad u joint.

Crawl under it in park and twist the drive shaft side to side. if there is any play the joints are shot. $25 at auto zone and 1/2 hour of time you will be fine.

Good luck.

 

[basketcase]

seems to be coming from the rear, i think. the front bearings are only a few months old.

 

[tch777]

I had something similar last year. For me it was the drivesaft out of balance and it wasted the pinion bearing. The guy who fixed it said I was lucky

 

[shane74]

My vote is a bad u joint.

Crawl under it in park and twist the drive shaft side to side. if there is any play the joints are shot. $25 at auto zone and 1/2 hour of time you will be fine.

Good luck.

Ditto.

 

[basketcase]

how can I tell if the pinion bearing is bad? Is it easy to change? the joints seemed tight when I twisted on the shaft, but I'm tempted to change them anyway. any idea what a driveshaft shop would charge to change the joints and balance the shaft?

 

[tch777]

It cost me 75$ to have my driveshaft balanced but I had the diff shop send it to the driveshaft shop to do it so I am sure it got marked up in somewhere.
My guess is it would cost you around 100 to 120 for them to balance the shaft and swap out u joints. They can also check your pinion bearing too.

Tim