I just remembered that I've also seen this with worn clutches. (on stick shifts)

Did you guys check your tranny fluids? If it is OK I'd say there is a problem with your torque converter or clutches in the tranny or similar. By all means take it to the dealer, and if the give you the run around take it to a tranny shop, spend the money for a diagnosis then shove the slip up the nose of the jeep dealership and ask for them to pay for that too.

 

I have a manual and i have had this happen twice going down the highway, for no reason it just starts shakeing like man, so i pull over check ever looks ok, get back in and drive away and its all fine

 

Wow! My wife likes driving in reverse too, but has never pulled on the highway in reverse. I can barely get to 30 without fishtailing wildly. Try using something like fifth or sixth gear in a forward direction & see if the shaking goes away.

 

I bet yall will find that it is more prevelant in Jeeps with the 4.10 gears. Mine has 3.73s and does this just a LITTLE bit. Having a trailer on or a load in the Jeep probably does amplify it some. I don't think it's anything to worry about. I think it's the driveline angle changing. The working angle of the driveshafts is designed with forward motion in mind. When you back up, all of that design theory is out the window. Reverse is also the lowest ratio gear in an automatic....usually in a standard too, but not always, so there is more leverage to pull the driveline out of proper alignment and cause the vibration. Remember too, it takes more horsepower and torque to drive an automatic. Standards usually have a little more leverage because of the clutch. Add a trailer or heavy load to the mix, and that amplifies it even more. It may have something to do with these CV jointed driveshafts. All this is just a guess, of course. I wonder if there's anybody on here with non stock driveshafts and an auto who'll chime in? Anybody?

 

Mine is not geometry shift. The transmission can't seem to choose how many rpms the torque converter will hook in at. If I try to climb my driveway very slowly, it will move then stop move then stop. A more assertive approach yeilds no slippage or shudder at all. I'm accustomed to axle wrap increasing as the torque is increased.

 

That almost sounds like a traction control issue. Have you turned it off and tried it?