Ok I have a 97 jeep wrangler 4.0 5spd and I am stumped, along with my friend who is a chrysler mechanic.
I get vibration between 30 and 40 while the engine is under load (accelerating, decellerating)
I have already:
replaced the rear u joints = no luck
replaced harmonic balancer = improvement, but still there
All wheel bearings are good
The right front wheel U joint is no good
wheels/tires out of balance.
The tires don't cause vibration till the highway (60mph +)
I don't think it is the front U joint because I only have a problem while it is under load in 2wd
Any more ideas?