Vibration

Its coming from the back half of the car.

Its NOT the bolts holding the driveshaft to the rear end. Those were loose a couple weeks ago, fixed that with some locktite.

My dad says the U-joints are okay. Theres no play in them.

I just drained and refilled the rear, and the only thing I noticed when I had it open is when I had it turned so that two of the spider gears were facing vertical they were sort of loose. I could wiggle them up and down a bit.

I ran the car in gear while on jackstands and it makes the vibration. The motor isnt rumbling around. The trans didnt seem to be moving around. I took the wheels off and could feel the vibration in the calipers.

It also does the vibration while coasting in neutral.

Were both pretty well stumped.

Did you check to see if a weight came off of the diveshaft? You can normally tell by the discoloration where the old weigh was in an area from 1/2" to 1" long rectangle shape. If so you should get the diveshaft rebalanced.

I swear I replied to this earlier but...

There are two quarter sized weights on the shaft up by the trans yoke. There doesnt appear to be any missing. Also the big weight is still on there as well, however, I can wiggle it around just BARELY. Probably not even enough to do anything.

Also, this vibration keeps going right up til the car stops pretty much, in fact its more like a slight clunking than a vibration.

I've been attempting to fix a similar issue.... just haven't got too far myself.

First thing, tires. It is amazing what 1oz of weight in the wrong place can do.... New/reballanced tires = 50% of vibration.

U joints, depending on mileage, can feel pretty tight, mine were original with 130-140k ish, had no slop I could feel.

Replaced them anyway since I had the driveshaft, replacement parts and a big hammer (big hammer not realy required)

That took out 40% of the vibration that I had left.

I can't see any issues with the weights on the driveshaft, but the quote I had to reballance it was $20-$30, so it's a done deal just to be certain that that isn't a source of the remaining vibes....

After that, tailshaft bearing.

Your mileage and equipment will vary...

I'm somewhat in the same boat too. Started as noise and vibration. First go was to replace the U joints, 100K on them. Bad vibs still there. Pulled the axles to find a destroyed bearing on the passenger side, axle chewed up pretty good too. Replaced bearings both sides, axle saver on the bad side. During this period I also installed CHE upper/lower control arms and the trans tail shaft bushing.
Noise better, vibration better but not gone. Only bad at 50-55 and up. Got a "good" axle at the pick n pull. New bearing. Checked the mounting bolts on the control arms, and tightened them to 110 lb-ft. Better but not there. Reclocked the driveshaft 180 degrees.
The vibration is much reduced and now slightly noticable at 70-75 and above. I'm still not satisfied though, so the search continues.
Next up is new tires (needed them anyway.)
I'm also going to rotate the driveshaft in the trans.
I should add there's no evidence of a missing balance weight on the driveshaft.

Well Im just gonna drive it for right now, hopefully within the next week or so Ill get it back up on stands and pull the axles. Its just too nasty out right now to do it.

I really shoulda done it while I had the rear end drained and open...

If you are hearing a "clunk" this probably won't help. Mine had what felt like a vibration when going down the road - cruising speed / part throttle. When I adjusted the tps my "vibration" went away. My daily rider / commuting partner would have bet his paycheck that I had U-Joints going out... Too bad he's on a leave of absence (as of today) or I'd collect!!!

B