I recently bought a 2001 GC and the front end has been making a humming noise. Its in the driveline and starts at 5mph and gets louder and faster as I drive faster. I thought it was the drivers side hub bearing so I replaced both the passenger and drivers side hub bearings, while I was there I noticed the cv boots were torn up so I replaced both axles while I was there. I thought for sure replacing all of this would get rid of the humming but it didnt.

This happens whether Im on the gas, coasting, or breaking.

I pulled the front diff plug off today and its full, it also had the typical amount of metal on the magnet.

I have been searching for hours but cannot seem to pin point my problem. I may pull the diff cover off tomorrow to see what the carrier bearings look like.

 

Sounds like a bad pinion bearing

 

Muffler bearings, gotta be!


No it sounds like your on the right track, pull the cover and have a look see. Worst scenario you'll be out some gear oil and a little rtv lol. Unknown noises are the worst! There's no good way to tell wheres its coming, it drives you nuts, and you always fear the worst. Good luck

 

I havent pulled the cover off yet but there is no play in the yoke that would suggest it would be the pinion bearing. I may pull the front drive shaft off to see if that could be the cause. But the boots on it look fine (mine has the CV style joints on both ends) and there is no grease on the floor boards.

I'll check the muffler bearings next

 

Haha I'd put my money on that

 

What's a typical amount of metal? Any more than a slight coating of dust is suspicious. Use a dial indicator on the pinion yoke. Those bearings are preloaded so there shouldn't be ANY clearance in the bearings. Zero! Once there is, they fail quickly.