Well for me it turns out that it was the u-joint, When i put the new rear end in i checked the u-joint not u joints.....I took it for granted that because the rear driveshafts rear u-joint was changed why wouldnt of someone checked if not replaced the one infront of it on the same driveshaft with the same miles & wear N tear, but no turns out my u joint that was up by the t-case still on the rear was shot, not 1 needle bearing left in the u-joint period i can believe something like this was missed by a mechanic & the machine shop that changed the first one the prev. owner had it changed so i would check that on your truck. I still just dont understand how the noise on my truck was here and there there when there was not 1 bearing left in the u-joint should of been making the noise the whole time i would think. hopefully you have the same easy fix

 

I have the same clunk as well. Far back as I can remember its always done it too. I'll shift it to reverse and wait for it to clunk in gear after about one second. Then get to going, never gave any problems.. I've had the rear end cover off before and everything looks great in there, I was surprised the first time a changed the grease in it, she has a posi-track in her. Not sure if it came from the factory that way or was added.

 

Ive had the same clunk. Ive dogged the hell out of her and shes still holding. I got AAA towing for when it does die/blow. Cant beat 70 bucks a year 4 tows.

 

I had both U-joints replaced alreday. Had a mechanic out here check her out,.....he seemed to know quite a bit about these blazers.....he didn't have much concern about anything on her minus the attachments to the frame from the body. They are kinda rusty and it might be that one day.....the body may separate from the frame. As far as the clunk....he just said it was slack in the transmission from front to back. She is just a used truck and is worn. No worries....willl run her until I get something else, or until she breaks on me. I think she will run pretty strong though, so will use her for commuting to work, and to haul around my windsurfing gear. Want to get a brushguard.....that will be the only addition I will put on.