I am having a resonating vibration in my 2001 4dr 4x4 Blazer with 93,000 that seems like it is coming from the rear axle. Had the wife drive it today while I rode in the back and the loudest area is coming from the back of the truck. The sound had started getting more pronounced a couple of weeks ago. It is mainly when you are driving above 55mph and gets worse the faster you go. I have put it in neutral while the noise is present and there is no change. To begin trying to figure out where it was coming from, I started with changing the rear diff fluid which had not been done for awhile . This did not help with the noise. The tires have been recently balanced, but I will check tonight to see if maybe I threw a weight. The next possibility I will try is to change the rear u-joints.

So I have two questions. First being if anyone has any ideas what the noise may be. U-joints, wheel bearing, rear diff/pinion, drive shaft out of balance, thrown weight on wheel? A better direction is what I am looking for.

The other would be how to pull the rear drive shaft? With my older S10, it was just unbolt the 4 bolts on the rear u-joint and slide out the drive shaft. On this one, original u-joints are still in place and I don't want to go beating on anything if it is the incorrect way to remove it. There is a rubber boot around the front part of the rear drive shaft, so I'm not sure if I have to remove that to expose something else or if this is just a dust/dirt boot. Any help would be appreciated.

 

It could be u-joints. Could also be wheel bearings. You need to verify. Jack the truck up and support the rear axle on jack stands. Then see if there is any up/down play at the wheels. Also check the pinion flange for up/down or in/out play. Do the same thing at the u-joints.

The driveshaft comes out the same as your older s10. 4 bolts and a pry bar. It'll then slide out of the back of the transfer case.

 

ah I am having the same problem. My wheel bearings in the front are worn out so this could possibly mean that all of my wheel bearings are going bad

 

Well I checked the up/down play on the rear wheels and there is very little movement. Both sides are very similar. I believe there should be some play allowed. Also, it didn't look like I threw any weights.

Unfortunately, we have company for the next couple days so I won't be able to try replacing the u-joints and checking the pinion flange for play. I sprayed some PB blaster on them to hopefully loosen the u-joints from the flange.

Any other ideas...or I will check back in with any updates (I mean successful repairs!)

 

Well all is good now. I replaced the rear drive shaft rear ujoints and the vibration is gone. Thanks for the help.

But while I had the drive shaft out, the ujoints in the front of the drive shaft (nearest to the transfercase) seemed to have more play in them than I think is normal. The question on replacing these is, can this be done at home or is a different press needed that would have to be done at a shop?

 

It can definitely be done at home. It is just a little more involved than the rear joint.

One word of caution that I will say up front. Mark the orientation of the slip yoke to the drive shaft. Misalignment up front can cause an imbalance. I just went through this on my dad's '04 K2500. He took it apart without marking anything and I put it back together. Needless to say, it vibrated and ended up taking out his output bushing in the back of the transfer case in the process.

You should mark the orientation on the pinion yoke as well, but this one is easy to change if you end up with a vibration.