I have a really bad rear end clunk when applying my brakes.
It is even worse when i am backing up.
I replaced the tranny mount. It still does it.

 

I've had this happen to me once, it was the brake shoes rocking in the drums. It needed brakes anyway so everything was changed and the clunk disappeared. The brakes felt fine before I changed them but they're better now.

Is it going to be the same thing you have going on? We'll see.

 

What condition are your ujoints in? Greased?

 

I just got the truck. I havent greased the u joints. Hopefully they have fittings.

 

I probably should say its a cluck you hear and really feel. It feels like the rear end of the truck is shifting around.