Clicking noise when accelerating.

intheair2nite

I recently had a shop fix some oil leaks that required they take the motor out to get to all of them. It has a 6.0 and is a 4x4. Turns out I even had a cracked part leaking transmission oil that was between the transmission and engine. They also were to service my transmission. I had several manifold bolts that broke and they had to replace. I now have a clicking sound when starting off with the noice slowing and gets quieter as I am under speed. It has a pattern so it doesn't appear to be something just rattling and it's not a cracking sound. It's like metal clicking metal as something is turning. It's underneath the truck around where the engine and transmission kinda come to gether. We put it on the rack and put it in gear and even power braked it and no noise. No noise under idle nor in neutral giving it gas. Funny thing when in reverse on an incline backing up and putting on the brake kinda hard it makes the clicking sound. In forward it only does it under acceleration. Any ideas. It's not a u-joint.