OK here it is. When going down the Highway around 60 mph my rear axle starts to vibrate. I can tell it is in the back because my steering wheel is not affected at all and in the rear view I can see the bed shaking and the cab being steady. So I researched this on here and already did the following: Had tires rotated and balanced, no better. Replaced driveshaft U joints, no better. What else can it be? It is quiet annoying!

Thanks!

 

Have you looked over the diff? Might check your pinion for excess play.

 

How do I do that?

 

So you had the tires rotated?
Does that mean fronts to the back and backs to the front?
Or was it a normal rotation where one front goes to the back, one back goes to the other side in the back, that back goes to the opposite front and that front goes to the opposite front?

I ask 'cause if it was the latter, maybe the tire that went from one side in the rear to the other side of the rear has a bent rim?

Or maybe the driveshaft is bent or imbalanced or the u-joints aren't timed properly?

 

It could also be bad wheel bearing, loose bolt on leaf spring or loose bolt on ubolts

 

I had the tires rotated at the store, so I think they went with the later version rather than just straight front to back. However a bent rim should/might show up when balancing the tires? Unless it can be balanced out I guess.

U joints timed? What is that? I installed them today and pushed them in just far enough to get the clips back in, all look to be pressed in the same distance. They are the greaseable kind and I greased them good.

Gotta check on the U bolts and leafs tomorrow I guess. A wheel bearing going bad should make noises though, right? Do I check those like I check the front, jack it up and see if the tire has play by grabing top and bottom?

I really would like to get to the bottom of this.

 

Could be missing weights off of the drive shaft. Or it could be out of time. I once replaced the u joints on my rig and took the driver shaft apart with out marking it and had to re-balance it. Or perhaps it's a bent wheel?

 

Marked the driveshaft before taking it apart.

What kind of shop could balance it though? That would mean the U joints need to come out again right?

 

When my rear wheel bearing went out it felt like I was going over a lot of little tiny bumps in the road causing a slight up and down movement in the rear. A few weeks later it started to make noise that sounded like my rear differential blew up, to the point that I disconnected the rear drive shaft and drove home in fwd.
Unfortunately the rear bearing is pressed on unlike the front. When I found mine I had taken both of the rear shafts out of the axle and I could tell the difference between the two. One had a small amount of play which is normal and the other had lots of play and when I turned it I could feel the bad bearing.
If you check them I would remove both sides so that you can compare them and see if you can feel grinding. You will need to bleed your brakes after you do this. A link to a fsm is in my sig in case you have never taken the rear axle apart.

Hope this helps

 

OK, here is some more (bad) news. I jacked the Truck up and removed the rear wheels. Put the tranny in neutral and now I get the following results: When I spin the left drum brake by hand, the driveshaft turns. When I turn the right drum brake by hand, the driveshaft does not spin. When I put it in gear and turn either drum there is a definite friction point. All this would unfortunately point to the differential, right?

 

sounds like a normal open differential doing its thing....

Make sure the drive shaft is timed properly, look it up.

you could also check your tranny mounts, and re grease your u-joints.

 

2WD have a one piece drive shaft so it is impossible for it to be untimed. I marked it at the differential before removing and I marked all other parts before replacing U joints. The only place it might not have gone in the way it was before is the tranny, with the splines it can go in any which way (STS), so that should not cause my vibrations.

When turning the wheels in the back in the air there is no grinding or so from the bearings.

 

OK, just got my driveshaft computer balanced. Wasn't off much and it didn't fix anything. I will in a minute go for a drive and have a friend look at the rear from a different vehicle.

 

i agree with whoever said to look into the condition of your transmission mounts

also, how old is the clutch on this? 5th gear is pretty hard on a worn clutch

alfio

 

Clutch was replaced around 10k miles ago.

 

and have your checked your differential fluid level or changed in recently?
-pinion bearing throwing any juice around?

with the rear on jack stands check the free play of your rear diff, it should not be overly excessive.

 

OK, took a drive with another vehicle looking. Of course the vibrations come and go and vary in severity when they are there. However the other car did not see anything unusual. So we jacked the truck up and spun the rear wheels up to 90mph, nothing gross there. Some minor vibrations but nothing more than you would expect with the wheels of the ground doing 90mph. Put a micro dial to tires and rims to check out of round and they were only off 0.011 inches, so nothing. Checked the tranny mounts, look good, move freely. Pinion has no play. Haven't checked the diff fluid lately but I did change it regulary. Moving the rear tires off the ground, pulling on them and so on, no play or movement what so ever.

Next I will replace the shocks. The Billstein I have on there are 11 years old and have 150k miles on them. I just keep throwing money at it I guess until it goes away.

Any other pointers?

 

I would say that your outer wheel bearings are probably bad. When i replaced the rear end outer bearings they were so bad that i could wiggle them a 1/4'' in any direction, its really hard to tell how bad they really are until you pull the axle out.

 

You were right. I took the rear bearings out today and they have quiet some play. So leasson learned is that those cannot be checked unless taken out. Fun part is bearings, all the seals and so on are $180!! At least I don't need new shocks, tested them today and even after 150k and 11 years they are still good. Billstein!!

 

Did you notice this all of a sudden or has it been a while since you had it up to that speed?

I think I would jack up the rear end and get the rears spinning. You might notice a visiual wobble out of one of the wheels or be able to feel (by putting your hand on the body) one side shaking more than the other. Could be a bent axle if you don't regularly drive it at highway speeds. Can you think of anything harsh happening back there? Maybe hitting a curb or rock at speed?