I recently purchased a 2004 Grand Cherokee from a private owner. After a while i noticed a slight humming/grinding sound at slow speeds and to a stop and humming at higher speeds. I had it diagnosed and it turned out to be a faulty front differential. I was lucky to find a used Dana 30 quadra drive vari lock that had been rebuilt and intalled it. soon after i noticed a humming noise coming from the right front side of the jeep so i replaced the wheel hub, still the same noise not different. What could this be? Cv joint? something else? Also the humming seems to get louder when i go over bumps at speed or when the jeep suspension goes up and down while driving.
If you haven’t already, check the rear differential. This can be an illusive noise. Just have the rear wheels put up in the air on a stable lift and put it in drive. If the noise is there, you will hear it, if not, you know it’s in the front.
Note: The last humming noise I had in my Cherokee, I was told 3 different things by 3 different mechanics including rear differential, transfer case, and rear drum break dragging. It turned out to be a wheel bearing on the front passenger side. Good Luck!
I’m not sure I’d describe the noise as a hummmm, but more of a RRRrrrrRRR which disappears at higher speed only because it is masked by the road noise and other things going on. It’s about the only issue I’ve ever had with any of my family’s Jeeps. (For the record, Dodge pickups and Durangos do it too.} The design of the rear axles is such that the inner race of the rear wheel bearings is the axle shaft istself. When the machined surface on the axle shaft(s) wears down, or the bearing(s) begins to wear out, you will hear RRRrrrRRR. I’m not saying that’s definitely your problem, but it is, unfortunately, rather common. The fix is new axle shafts and bearings. Shop around. The shafts are WAAAAY to expensive from Jeep. The bearings can be bought at any auto supply. You also have the option to listen to it for a while. My Daughter’s '97 JGC made that noise for 20 or 30K miles. She sold it at 175K still noisy.