All of the sudden when I go from drive to reverse I hear a thud from the back of the Jeep. Does not happen when going from park to reverse. Is this normal and I never noticed it? It seems to come and go. 2008 2DR auto..

 

Lots of automatic vehicles do that, and never have a problem. If it's real loud, it could be an indication of a problem.
Can't say for sure if mine does it, too. I'll check in the morning.

You hear it from drive to reverse because, in drive, all the drive train backlash is pulled in one direction, then, when you go to reverse, all the backlash is pulled the opposite way.
In park or neutral, the drive train is at rest.

 

Ok thanks, was worried a driveshaft was on its way out..

 

It wouldn't hurt to look things over, though.

 

What am I looking for? I had my friend who is a mechanic look as I did it and he said he did not see anything abnormal..

 

That would qualify as having looked things over. You already had it covered.

 

Well now it's doing it even when going from park to reverse??

 

Does this only happen when youre parked on an incline?

 

Nope, level ground also. Hard to say where under the Jeep it's coming from, front or rear..

 

Hellhound before you go nots check your driveshaft make sure it is sitting in tightly on the yoke ends also check for play in the shaft you know get under the jeep and see if you can rock it or move it, most times that's what the thunk is, but if it seems ok then the next thing is have the tranny looked at. Oh is it standard or auto? Can Make a difference let me know if this helped.