First off I have to say this is a great forum with lots of great information. I did a search and founds lots on vibrations in TJ's but none like the vibration I have in mine, I have a 98 TJ sport that is stock, automatic, 4.0, no lift and stock tires it has 83,000 KM. I first noticed the vibration when pulling away from the stop sign and is around the 1500 RPM range, only under acceleration not when coasting, the vibration is noticable in the fact the mirrors vibrate and you can feel it in the seats and dash, here is where it is different from other vibration questions, if I put it in drive and hold my foot on the break and hit the 1500 rpm range it will vibrate, with no forward motion, and if I put it in park or netural and rev the engine there is no vibration. What do you think is causing this vibration? Also what RPM should my TJ idle at? and how can I set my idle speed lower? I am always haveing to ride the break going across parking lots, I can reach speeds of 15 mph without touching the gas peddle.

Thanks in advance, Danny.

 

A bad flywheel(unbalanced) might do something like that. Is the vibrations just specifically to RPM ranges? If so I would say flywheel or crankshaft.

 

i have a 97 tj with the 2.4 4 cylinder and manual tranny and i get the same thing when in gear and above say 1500rpm approx, i get a bad vibration, i also get a ticking noise which i believe i have narrowed down to the heat plate above exaust (haven't had time ti fix yet) the vibration stops though once i get to coasting speed or 2500rpm approx, again this only happens when moving, even if i put clutch down and rev engine while moving i hear, but not when parked. any help would be appreciated

 

Check the U Joints
I had the same problem and it turned out the U Joint went. The needle bearings were powder.

good luck
:)

 

If it only happens under load without moveing it has to be in the motor, try a good injecter cleaner and a tune up (plugs wires cap rotter) maybe even a new coil. Let us know what you endup doing.