Differential humming

[lmitch]

my 2000 has been making a loud whining/humming sound for a few months - on a tip from a friend, i took it to a tranny guy to check out the transfer case, but he seems to think my problem is up in the front differential.

anyone ever had a differential replaced? how much $ are we talking, worst case??

[scuba4321]

not sure on the cost, should be able to have it rebuilt cheaper than new. have you pulled the cover off, or checked lube level yet?

[JDPascal]

welcome to the forum lmitch.

Could be in the front driveshaft too........

The diff overhaul will run about $100 for bearings and seals, $35 for a shim kit if the replace the ring and pinion, $300 for a ring and pinion (max), $10-$15 for synthetic gear oil and maximum 8 hours labour at your going area rates. Take your pick of any combination of the above for lesser problems.

Have you checked the wheel bearings yet??

JD

[gtmud]

To assist in isolating your problem, pull the driveshaft from the front axle. If the noise goes away you may be looking at the T-case. How many miles on your XJ. I have over 93K and the T-case is working fine(avid off-roader)
Like JD said, look at your hub bearing assemblies, a good way to see if their going is if they are "leaking" fluid. These are sealed assemblies, so when they start leaking fluid, its getting ready to go. Average price $115 Advance auto. I have a hrad time beleiving your diff would need any work on it. Mine has been used and abused and still working fine. Running synthetic fluid. If it is your hubs, a couple simple tools,( 13mm 12 pt, 1/2" drive socket, a 36mm socket, 1/2" drive, 1/2" breaker bar w/ pipe, pliers, and a little muscle, you can do the change your self.

[Traktor]

What type of transfer case do you have? If it's a ZJ or WJ and you have a quadra-trac style case, then you may be looking at a worn out front differential due to uneven loading of the transfer case. The quadra-trac cases will 'lock-out' if they sense different speeds in the front and rear driveshafts. If your tires are badly worn or worn differently in the front and rear, then the transfer case may be attempting to lock-out the front driveshaft which can overload the frond differential and cause noticable humming. This could also happen if you've ran an off-size spare on a quadra-trac. This happened to my ZJ with a NP249 case which is prone to VC failures (the VC is the viscous coupling that acts as a limited slip component of the limited slip differential these have). If this is the case, you may only need new bearings in the front + labor. The gears in mine weren't bad, but the bearings were shot.

[MagicRat]

I agree......the wheel bearings do wear out and make the noise you describe, but the front gears should last the life of the vehicle.

[rotorfloat]

maybe it hums because it doesn't know the words...