I have a 99 Explored auto/4wd. A few weeks ago there was a hum begginning to come from the front end. Tires were shot, so I replaced them.
Then the noise went from a typical wheel hub bearing noise (hum from 0-40mph) to a really loud hum noise that doesn't fade out until 70-75 mph.
Previously, if I loaded either side in a turn, I could not differentiate which side it was comming from - just front end. When the noise worsened, I could load it so that the noise dissapeared on right hand turns. So, I replaced the rt frt hub bearing. Noise is still present, just as loud.

Other points I noticed:
- when in 4wd on a hoist, frt diff is noisey, rt frt wheel does not spin
- when in 4wd on dry pavement and turning, driveline does not bind
- when in 4 lo and slow coast, slight accel makes the drivetrain clunk then accellerate

I have searched the forums, but found no matches to all these conditions. Any insight would be appreciated.
Thanks,
Jeff

 

I had the same problem with my 97. It's a rear wheel bearing. The change in noise is because you put new tires on which are a little bigger and a little heavier. Believe me you cannot tell where the noise is coming from the front or rear. I drove the car for 2 yrs like this. No play in any of the bearings. Finally the noise changed slightly. I said let me have another look, and low and behold the rear bearing had slight play. Replaced it (around 70 bucks on ebay) and the dreaded noise went away. I mean a real loud airplane landing sort of noise. I was ready to change the front differential. I swore it was in the front. Thankfully I didn't. All the wheel bearing are subject on explorers and mountaineers, finding which one it is can be the hard part. The key is when you turn one way the noise stops.

 

you have several possibilities. the front hubs, the rear axle bearings or the differentiaal / pinion bearing. it is hard to figure out which one is the problem. all you can do is look harder.

 

Well, through loading and unloading each side I had determined it needed a rt frt wheel bearing. So, as stated, I replaced it. No change in noise. I feared the frt diff was going. I had a technician friend of mine spin it again on a hoist, and he said left frt bearing. Having my doubts, I changed it last night. I'll be damned, noise is gone.


Keep
It
Simple
Stupid

I probably didn't need the rt frt, but it's in. I've never seen a bearing act like that, but i'm happy I'm out of the woods for $225.




Thanks for the effort guys.

 

the idea of turning and see if the noise goes away, then say its the other wheel works about 50% of the time. i could guess from my house and give you those odds. LOL
its is best to change out both hubs if your 100k miles, or 10 years old. They dont last forever.