Vibration

Bthompson

1990 B2200- getting a bit of vibration once I hit 45mph but vibration is only present when accelerating and immediately stops when I let off the gas. My initial inspection found a bad drive shaft center support bearing. But a new replacement didn't fix the issue. Bad motor mounts? Transmission mount?

Mrcrowley

Bthompson it's u joints most likely that was my problem anyway

MazdaMitch

Who did the center bearing repair?
You?
Reputable shop?
When repairing THAT part of the driveshaft, you have to mark it before dissembly and put it back like it was on reassembly to keep it in phase.

Also when replacing the universal joints, if you get crazy you can bend the tangs on the driveshaft.

Both of these can cause vibration.

Bthompson

MazdaMitch marked all components with paint marker and lined back up when reassembling. U joints seemed good as they didn't have excessive play or binding so they weren't changed. I am able to rotate the entire driveshaft back and fourth, approximately 1/8 of an inch. Bad differential?

MazdaMitch

Nah not a bad diff.

Maybe it's your wheels out of balance.

OGMB2K

Getting back to your problem ... you mentioned it vibrates under acceleration @ 45mph, is the vibration speed related or does it occur only under torque?

For example, a wheel needing balancing will usually only shake in a certain speed range, usually the range the machine uses to locate the weights location. Drive shafts also need balancing, would it be impossible for the driveshaft to have to be re balanced?

If it ONLY happens under acceleration, then something else could be causing this vibration.

kz6fittycent

OGMB2K No it's not impossible to get the driveshaft rebalanced. That said, you're supposed to put them back in the exact orientation they came off.

Vibrations under acceleration can be caused by a lot of things - to include a bent driveshaft. But that should not be the first assumption unless the vibrations appeared AFTER a change to the driveshaft or associated components (e.g. u-joints, bearings, etc). You can put your truck up on blocks and put the truck in gear and watch the drive shaft spinning - looking for anything obvious.

That said, even a stuck caliper can cause vibrations under acceleration. There are a lot of things that it "could" be. It's going to be a process of elimination.