Hello and welcome.
When in reverse does it only make the noise and feel on the initial acceleration, or will it continue as you keep backing up?
It only makes the noise and jolt on the initial acceleration then goes away.
You may just have a bad u-joint. Get under the truck with it in park and not running and grab hold or the driveshaft and try to turn it either direction, back and forth. Also grab the front and rear and try to move the driveshaft up and down. Look at the front and rear to see if there is excessive movement.
2. A bad engine mount or transmission rear mount. The drivetrain will move one way in drive and the other in reverse so a bad engine mount will let the whole drivetrain move up in reverse, but not in drive. You would need someone to put the truck in reverse, foot on brake and hit the gas a little while looking at the engine or rear trans mounts to see if everything is moving / jumping. Go from reverse to drive and look for a difference in the amount of movement of the trans and engine.
Could the rear output slip shaft splines be dry on the transfer case causing this to lockup.