BAD Vibration in rear end

[96GMC2500]

Hey everyone, I'm looking for some help trouble shooting a wicked vibration in my truck.

It's a stock GMC 2500 crew cab, long box. The vibration starts intermittently, anywhere from 30 - 70 Kph, dosn't go away if the trucks in neutral or not.

Just had it at the tire shop, they couldn't find anything. They wanted to take the diff apart to see if that's the problem, but I brought it home to diagnose on my own after I did some research.

So far I can't find much on the subject.

it feels like a separated tire being driven on at highway speeds. The vibration is pretty severe, loud noise in the cab, feels like the truck is jumping. Stopping and starting dosn't change in, although if it sits for a day, it won't do it.

It seems to only happen after the truck has driven a few kilometers.

So far I'v looked underneath and been able to identify that the center shaft bearing is slightly worn and cracked. It has some play in it, but not a lot. Maybe 1/4 to half an inch. The rubber surround is definitely cracked, but not separated.

The tire guys said they checked the u joints, but I'm not sure if they want to get the truck in to rip the diff apart so they can hit me with a big bill. It's my wifes truck, so maybe they assumed they could pull one on her and make a quick buck.

If anyone has any idea's, or suggestions, troubleshooting tips, etc, or even a thread that already exists regarding this problem, that would be great!

Thanks!

 

[PlayingWithTBI]

So far I'v looked underneath and been able to identify that the center shaft bearing is slightly worn and cracked. It has some play in it, but not a lot. Maybe 1/4 to half an inch. The rubber surround is definitely cracked, but not separated.

That would have been my 1st guess.

 

[Frank Enstein]

What he said!

 

[96GMC2500]

Right on, thank's for the verification! It's been a while since I'v pulled a drive shaft. Is it a fairly simple process? I'm sure I can find some youtube videos, but it's good to hear from people that have done it.

I'm guessing it's a good idea to change the ujoints out while I have the driveshaft out too?

 

[red98]

Right on, thank's for the verification! It's been a while since I'v pulled a drive shaft. Is it a fairly simple process? I'm sure I can find some youtube videos, but it's good to hear from people that have done it.

I'm guessing it's a good idea to change the ujoints out while I have the driveshaft out too?

If they need changed, don't think they're that much of a pain to get to especially rears. I think they're $30-50 each so no need to throw away $.

 

[96GMC2500]

Is it all the same U joint? Like the front is the same as the middle, which is the same as the back.

 

[stutaeng]

That center support bearing is a pain to remove if you don't have a press. I changed mine on my 99 NBS and was cutting and cutting with an angle grinder until I was able to remove it. Not sure if the 400s are the same. Changing it along with U joints if they have play would be a good start.

But why do you say vibration is still there if truck is in neutral? That wouldn't be be driveshaft related then, right?

 

[Pinger]

But why do you say vibration is still there if truck is in neutral? That wouldn't be be driveshaft related then, right?

It would be. The disconnection of drive is in the gearbox - upstream of the shaft.

 

[Dariusz Salomon]

One thing to do to take tires out equation is to put the spare temporarily first on one then to another and see if it changes anything-or if you have 2 extra wheels put those on.