Ok so for the last 2 days I noticed a slight vibration and rumble sound coming from the rear of my 98 blazer. It was pretty slight at first and I could not identify it at all. I thought I heard it only when I had it at a certain RPM or when I was giving it throttle.

I first thought that my exhaust was loose and leaking and was vibrating at a certain RPM. I guess I was wrong cause last night the rumble got worse.When I wentto drive it I wasn't even able to go 50 ft.and had this awful clunk and clang that shook the whole vehicle. It happened at every rotaion of I guess the driveshaft or maybe the wheel or axle shafts. I can't tell what it is. It was dark when It happened and started to rain.

So I'm guessing driveshaft, axle, diff, t-case or maybe trans. It feels and sounds like its more from the rear than center of vehicle (trans.) but, it clangs/vibrates more in drive than in reverse and a little less when in neutral ( I coasted down a hill). I took a quick look under last night and nothing seems to be loose that is visible.
So I know it might be vague but what thoughts do any of you have??
Its a clank and vibration at every rotation and I can't even drive it now. thanks.

 

U -joints....

 

Ok so I just took a look under the vehicle and had someone drive it slowly to see whats up. The clunk is coming from the back of the driveshaft or diff. It shakes a few times per wheel rotation. I can't tell if its the diff. gears clunking aroundor the driveshaft u-joint.

If I remove the driveshaft clamps from the rear diff., will it slide out of the slip yoke?... so I can drive it 4wd to the mechanic. Then I can also see if its the diff if it still clunks.

 

If it is the diff, removing the driveshaft might not make any difference... I would drop the rear diff cover to have a look inside first. That will dictate how you should get the truck to your mechanic.

If you hear the noise a couple of times per wheel rotation, I would bet that the pinion gear has lost a tooth.

As far as just removing the rear driveshaft and driving it like that. Expect to loose transfer case fluid on the way over... The outside of the slip yoke that goes into the back of the transfer case is the sealing surface...