I have been away for awhile. My comet has big vibration when going about 55-60 mph but levels off at speeds greater than 65 and up (just doing some testing) around town speed around 25to 50 it's fine. I guess the question is does this sound like a slightly bent or out of balance driveshaft or something worse?
Sounds like old, dry u-joints. Replace them before you lose your driveshaft and note that the front and rear are different sizes.
i'd definatly check the u-joints. my car had vibrations at different speeds and i pulled the shaft, opened the caps and the needles were destroyed and all over the place inside
Most of the problems I've had like that are because of a tire seperating. Just replaced 2 on my Montana 2 days ago.
for me it was the trans mount. i replaced the u joints and checked the drive shaft, all were good but it still vibrated from 50-60. once i replaced the trans mount it was smooth as silk again.
When its vibrating the worst, kick it into neutral and see if it remains. If so, pull the drive shaft and get it checked for straightness and balance.
You may have lost a weight off the driveshaft.... Can you pinpoint where the vibrating is coming from?
Improper pinion angle/trans tail shaft angle will do it also.Especially if you have swapped the engine/trans combo or rear axle recently to something not common in a mav...like an FE motor and a C-6 trans.Check all the other things first...
mavman is telling you why my trans mount made it vibrate. when i pulled the old one it was worn to where the bolts were almost half an inch to the passenger side off. this caused the tail of the trans to be off by over an inch. the mount is about $50 and mostly easy to replace. i did the u joints and tires first then had my drive shaft checked (which ended up being straight and balanced)
This is one of those fun ones...trying to track down a drivetrain vibe. Funny thing is, it is good for you. You end up replacing a BUNCH of worn out stuff before you finally find that it was a combination of ALL of those items... I ended up doing a driveshaft balance, new u-joints, new tailshaft housing, bought (but didn't use) pinion angle shims, balanced rear wheels, I think there was more but it has been a while, and I don't remember what else it was.
