I got a 97 SE 4.0 AX15 with 33's" and stock gears about 160K on the odo if that matters. It just developed a shake when the vehicle is accelerating maintaining speed up hills. Doesn't do it clutch in moving revving the engine, nor sitting at idle no hesitation under accell either. Starts up first time no problems. Shake/vibe is the same at all speeds any gear altho a little more pronounced in 3rd. Almost feels like a miss, but with no hesitation or problems at idle I don't think it is. Last tune up done ~8000K ago, Trans fluid changed ~2000K with 10W-30 semi syn. 33's and aluminum rim installed ~500miles ago. I haven't started to diagnose any more than I noticed driving around, not really sure where to start. I m pretty handy with a wrench and have a FSM.

 

Went to the parts store no CEL and no codes on the scanner. I'm at a loss, and apparently so are 40 other people. I'm thinking maybe drive shaft suddenly went out of balance. But shouldn't the Jeep shake whether it's under power or coasting if it were?

 

I've had driveshaft u-joints vibrate under power but not when coasting. Any of 'em feel rough or loose when you turn them?

 

Driveshaft is nice and tight, very little play maybe half inch or less side to side. Would larger tires change the DS angle? I don't think tires alone would, but I never did drop the trans when the lift was put on a few years ago. I noticed this am on the highway the shake is related to speed. I also noticed the exhaust note was a bit louder than normal. I noticed last oil change my muffler was getting in bad shape. Would a hole in it be able cause this?

 

I want to lean towards u-joints as well. How much lift do you have?

 

I'm starting to think U-joints as well. Now that there a few more miles on it is starting to make a growl and thunk over bumps from the back. I will get to that this weekend I guess. I have a 3.5" all the way around