Ok i have read as much as the search would let me, I have a 95 automatic
and when i let off the gas i get a clunking noise, I check driveshaft u joints
and well there tight. I did change the transfer case fluid and glad of that it was low and black. Well took it for test and still does it.
I here grease the slip yoke but can't find anything on that, Do i have to take off the drive shaft? if so i will get new u joints and do it the same time.

 

Did you install a lift recently?

 

No lift or anything newly installed.

 

Could be something broken in your transfer case. Or how about your rear diff... do you have a locker? Something broken in your diff could cause this too. Is it rhythmic thumping that changes with speed, random clunking, or just a couple clunks and then it stops?

 

Mine does that a little too. I found that I have the slightest amount of play at the front pinion yoke.

Try grabbing the yokes and see if there is any play whatsoever

 

Could be as simple as a dry slip yoke. When they dry out, they'll stick and make a sound like that. If you're lucky, there'll be a grease fitting on the slip yoke, if not, you'll need to drop one end so that you can get the two pieces apart to grease the splines. No need to drop both ends unless you're going to do the u-joints while you're there.