Bad vibration at rear tires, but tires are not out-of-balance

[chemman]

I was driving my '94 250 automatic trans diesel truck, at 50 mph &
was in overdrive, on smooth blacktop road. All of a sudden the
seat started vibrating very badly, indicating that to me; that I'd possibly thrown off a wheel weight (like a tire was out-of-balance), I stopped & checked everything rearward out & found nothing wrong!
When I started driving again, there was a slight vibration, as before, & when I reached about 50 mph, it ran smoothly again (just like nothing wrong or had happened earlier)..
I was wondering if it could possibly be a bad bearing in the rearend or axel bearing going bad? Also could the vibration be caused by a dirty or partially plugged transmission screen or something in the transmission?
I can remember having this type vibration only once before, but it was in the front end (tie rod ends were worn out), replaced them & no more problems with vibration, until now..
Does anyone have any suggestions or cures for what's happened to cause the rear end vibration?
Any help or ideas would be greatly appreciated
Chemman

[aceohearts]

Check the u-joints...

Park with the tranny and transfer case in neutral, and set the parking brake. Laying under the truck, grab the driveshaft and wiggle it up and down and side to side. Also rotate it. Watch the u-joints as you do this. Any, I repeat ANY movement in the joints and they should be replaced. When they go bad they can cause a hard vibration in the driveline...

[Greenie]

I chased a high speed vibration for a couple of years before discovering the tires were at fault. I jacked up all 4 wheels, put it on stands and in 4wd and drive. I watched the tread as the tires rotated and saw an inch of side to side on the treads on 2 tires. I mistakenly thought that was acceptable and moved on. If I had to do it all over again I would have replaced the tires sooner.
The truck is smooth at high speeds with new tires.

[cdnsarguy]

chemman

Please be so kind as to put much needed info in your signature, go to "My Home" at the top of the page then "Personal info" click "Edit" put "all known" particulars for your truck/van in the signature block, any other info you feel worthwhile in other parts of this area. Fill in the "geographic location" too it is just as important, members can then direct you to the best known suppliers for parts, repairs, fuel etc closest you by location/ area/country. You could be just around the corner from a member willing to assist you or a parts store with what you need..
THANK YOU

If you have a supercab check the center hangar bearing for bad bearing or weak rubber also a dry slip joint.

[sbbamafan]

My vote is for u-joints. I had similar problem and replaced them all. Now the big beast drives (sort of) like a limo.

[chemman]

I'm sorry about not putting in the "particulars" of my F-250, I just forgot all about it..People need info in order to help someone, Thanks for reminding me..I really appreciate the help from everyone, because I'm "a diesel dummy"& know very little about them..lol