Im asking this for my friend, he has a 2003 jeep tj sahara edition that is lifted 4" on 33's, it s a 4.0L manual.

The problem is when the jeep is moving forward but not accelerating there is a really loud grinding noise that seems to vibrate the floor boards as well. When it's accelerating it doesnt make any noise, but when slowing down it makes the noise and the whole jeep vibrates, the faster your going the louder and more violent vibrations you get. It doesn't matter if its in gear or not, or if your foot is on the clutch or not, if you put it in neutral and coast it will still vibrate and scream at you. WTF is this? I guess maybe bearing? anyone had this before? seems to be coming from a central location on the jeep, not up front or in the back particularly.... oh and also, it happens whether its driving strait or turning, doesn't matter.

any advice would be great thanks.

 

Does he have an SYE on there? TJ rear drive shaft is super short and has the same hare-brained slip-yoke on the transfer case output shaft like XJs do. I'd also really look at the U-joints

 

the u joints are good, he might have a SYE it's over 3" lift, t-case is dropped a bit too, would it be the SYE making that noise?

edit- he changed his u joints about 10,000 ago i think

 

WAIT! would his t-case be pooched because he drives around in 4wd when he's not supposed to? (like on dry cement) Is that the noise? The slip yoke grinding?

 

If he's dropped his tcase I doubt he'd have an SYE on there. It could be the slip yoke indeed but that's normally unrelated to using 4H on pavement, usually u-joints and the tcase chain blow up for that. Normally the slip yoke will cause clunking when it isn't greased up anymore.

Which U-joints did he change? Also, does this continue if he puts either the tranny or tcase in neutral?