Hi I just bought a 89 Cherokee last week. It has a hum in the rear end like a tready tire hum But it goes away when I let off the gas. So I was just wondering if this is something that I need to worry about or is it normal. Thanks for your time

 

It sounds like it could be a gear or bearing in the rear diff.

 

That's what I was thinking to if I put some good fluid in it would that help it

 

A hum, could be a number of things.
Depends on the location of the noise, the intensity and a few other things, like weather, age of parts/vehicle, mileage, last checks on the engine, tranny, tc, brakes, etc...

But, just a guess, a hum from the rear sounds like, it could be that your 4wd is engaged and your just driving around with 4wd all the time.

Mine has some road noise/hum when im using it. And goes away when i go back to 2wd.

Does your vehicle have 2wd selc-trac or is it 4wd all the time? Might make a difference, if you can determine what kind of engine, trannsmission & tc you have.

 

Yeah I have 2 wd if that's it,how do I get it back to 2 wd

 

check your linkage, see if its tight or loose, from the handle to the tc...
another way is to put it up on jacks and check to see if the tires spin independently or not.

i have similar issues - mine is picky, wont disengage for like 5m-30m after i disengage it. i check the linkage each time i have to use it, its always right. but never stops when i tell it to...