I've got a new noise in my '99 4.0 and I could use some expertise in helping diagnose it. The oddest part is that it only makes this rattle on flat ground or if the nose of the jeep is pointed upwards. Does not make the noise going down a hill or if the backend is slightly higher than the front.
Ignore the lifter/piston slap knock which does go away once the engine warms up.
- Engaging the clutch has no effect, so seems like it's not the transmission or transfer case.
- I removed the serpentine belt and ran briefly thinking it might be the water pump, no change.
- It makes the noise regardless of engine temperature, but recently has gotten more pronounced on cold start for a few seconds.
Ignore the lifter/piston slap knock which does go away once the engine warms up.