4 Wheel Drive/SUVs: 96 JGC Front End Hum/Vibration, auto transmission fluid, wheel vibration

Question
Hey Carl - I have a 96 JGC Selec-Trac 4x4 that has served me well up to 103K miles.  No problems at all.  I take meticulous care of it, go offroad 2-3 times a year (about 500 miles), and tow 5000 lbs 8-9 times a year, for about 3000 towing miles annualy.

The Jeep has been garage-kept for its entire life, but its been outside for about 5 months as I am at a temporary job assignment.  About three weeks ago, just as it started getting cold outside, I detected a noise coming from the front end.  It starts at about 25 MPH and continues in intensity and pitch up to about 70 MPH.  Around 40-50MPH it is accompanied with a minor steering wheel vibration.  The pitch and volume of the noise increases with road speed and is independent of engine RPM.  I have put the Selec-Trac in 2HI, 4HI-FT, and 4HI-PT and neutral (coasted) and the noise doesn't change at all.  I have also put the automatic transmission in neutral (at speed) and the noise doesn't change.  The noise/vibration is steadily getting worse.

This weekend I changed the front diff, rear diff, and transfer case oil, which looked fine after about 20K miles on it.  The Auto-Transmission fluid looked new so I didn't change it.

About the only other thing I noticed is that my tires are very worn.  So I ordered a new set from Tire Rack, because I needed them but also because I'm hoping the tires were making the noise.

Any ideas?  I'm ready to take it to the dealership, but I wanted your opinion first.  If the front differential is the problem, how much should I expect to pay for a front differential replacement?

Kevin

Answer
Kevin,

It sounds like you may need to have your front bearings replaced, or at least checked, and re-packed with grease.  Since the noise seemed to get worse due to the cold weather, I would highly suspect that the front bearings may have some moisture in them, which would contaminate the old grease.  Depending on the way the tires were wearing (on one side only, or evenly), may show that you need a front end alignment.  It wouldn't hurt to have the brakes checked at the same time.  I would doubt it very much, if you need to replace the front differential.

Carl