Hello all. New to forum. My Jeep is a 1999 XJ 4wd 4.0 Automatic and only 94k miles. Bought brand new and kept up with all maintenance religiously. Its like one of my kids!!!! Anyhow, recently the drive train is making a "new" very audible whining noise. Hard to describe but sound like it does when it is in 4wd low. However it now makes this similar noise in 2wd mode! As soon as it shifts out of first into second, the noise instantly disappears. It does not make this noise in any other gear including reverse. Just in first. If I shift to low1 it will make the noise continually. It shifts perfectly with no slippage. I have pulled a pop up over the summer twice and havent had an issue other than the noise. Was going to take it to a Jeep dealership but wanted to get a few opinions first and see if anyone else experienced this issue???

 

Sounds like compression braking. Let off the gas when in D and 1st gear and see if your body lurches forward. You shouldn’t have compression braking when the shifter is in Drive, but you should have it when 1-2 is selected on the shifter

 

It makes the noise just as bad when accelerating so that wouldn't be it.