theres a loud clunk when i put it in reverse like its engaging real hard what would cause that

 

Either its bad u-joints,rear end,or trans. Check the u joint for wear/play 1st before anything. if that turns out good,jack truck up,add safety jacks,remove the driveshaft. then reinstall it to the rear diff only. turn the driveshaft back and forth to see how much play you have before the wheels move.

 

i just replaced the back u joints could it be the front ? also its a diff trans and rearend

 

Check transmission linkage, and I would pull off the rear differential cover and see how the gears look in there. Plus it wouldn't hurt to change the fluid.

 

ill check and get back to you