Hey guys... I've been having a bad vibration at 50-80 MPH since I got the truck. It has 50K miles on it. Autotrac t-case. The vibration feels like its coming from the rear. Tires are all "round", and freshly balanced. I changed the u-joints, they seemed fine but I did it anyway.

Before I popped the driveshaft off, I ran the truck with the back wheels off the ground, and in 2wd, and the vibration was there, and really bad. Tried it with the driveshaft off, and in 2wd, and the truck vibrated almost as bad as though the driveshaft was still on, and the wheels were spinning. Do I have a bad bearing in the t-case? It shifts and works fine, just this bad vibration.

Help please!!!

Hey guys... I've been having a bad vibration at 50-80 MPH since I got the truck. It has 50K miles on it. Autotrac t-case. The vibration feels like its coming from the rear. Tires are all "round", and freshly balanced. I changed the u-joints, they seemed fine but I did it anyway.

Before I popped the driveshaft off, I ran the truck with the back wheels off the ground, and in 2wd, and the vibration was there, and really bad. Tried it with the driveshaft off, and in 2wd, and the truck vibrated almost as bad as though the driveshaft was still on, and the wheels were spinning. Do I have a bad bearing in the t-case? It shifts and works fine, just this bad vibration.

Help please!!!

Did you have the driveshaft balanced with the u-joints, that may help. Is the rear end fluid and xfer case full. Your xfer case should have the blue autotrak II fluid 2 qts at the dealer. If you are sure it is the rear causing it look at the rear disc/drum - my 01 had oval drum sections but straight discs and you could see them at an idle mounted with a few lugs and no tires on when the rear was jacked up. As to removing either shaft and running that alone will cause a complete drivetrain out of balance with the clutch packs in the xfer case so that test will not work. Also when you said round, were the tires "Force" balanced with a machine that has the drum putting pressure on the tire checking it - 1 out of 10 tires are out of round or even out of balance spec - lots of weights are a clue. Doubt its shocks on an 02 unless you really beat the Blazer offroad but look for leaks.

remove the driveshaft, spin it 180, and reinstall it.... if its the driveshaft, that might help

I can't see it being the drive shaft since he ran the truck with it out and it still shook.

I don't have any ideas here myself

Hey guys... I've been having a bad vibration at 50-80 MPH since I got the truck. It has 50K miles on it. Autotrac t-case. The vibration feels like its coming from the rear. Tires are all "round", and freshly balanced. I changed the u-joints, they seemed fine but I did it anyway.

Before I popped the driveshaft off, I ran the truck with the back wheels off the ground, and in 2wd, and the vibration was there, and really bad. Tried it with the driveshaft off, and in 2wd, and the truck vibrated almost as bad as though the driveshaft was still on, and the wheels were spinning. Do I have a bad bearing in the t-case? It shifts and works fine, just this bad vibration.

Help please!!!

A good wheel balancer link.
http://www.gsp9700.com/pub/search/findgsp9700.cfm
MT

I'm pretty sure its in the transfer case, not further back.. Why would it vibrate just like it does going down the road, but with no driveshaft or anything on? I'm changing the autotrac fluid this weekend, so we'll see what happens.

Is the whole motor shaking? Could it be motor mounts?

Is the whole motor shaking? Could it be motor mounts?

Its not engine / rpm related. Its definetely speed related, you can put it to 5,000 rpm in neutral and its totally smooth.

Ended up getting the driveshaft balanced and new u-joints, seems pretty good now, still a bit of a vibration though, but I'll blame it on tires.

Ended up getting the driveshaft balanced and new u-joints, seems pretty good now, still a bit of a vibration though, but I'll blame it on tires.

Threads merged. Stop posting duplicate threads in multiple forums.