Possible rear differential? Transfer case? Help if you can...

[pixelflash]

I have a 98 Ford Explorer 4.0 SOHC with 95k miles on it. I have been hearing a whu-whu-whu sound for about 3 months now but was not sure what it was. Lately, I have been feeling a slight vibration in the floorboard and pedal that pulses slightly in time to the noise. I took it to a local mechanic that I trust and he said my rear differential is bad. He said he was not sure if it was the spider gear, rack or what until he pulled it off.

My question is this: if I'm feeling it up front near the driveshaft (I assume it's in the driveshaft since it feels like it's under my feet and not in the steering linkage), could it be the front diffy? Or maybe the transfer case? I am also thinking about taking it by the dealer to get a second opinion.

It also makes the whu-whu-whu noise stronger when I give it gas. If I let up, so does the noise.

Has anyone had experience with this?

 

[Bronco638]

I've experienced this, on my '66 Shelby GT350. It was a rear axle bearing gone bad. I wouldn't be surprised if you have a bad bearing somewhere.

 

[pixelflash]

Well.....here's an update. I've been wondering if it might be a bad wheel bearing. Before going home last night, I racked the wheel back and forth - slowly - while going about 5 mph in the parking lot. I noticed that when I pulled all the way to the left, there was a clunking noise from the tire area every few seconds. Then when I did the wheel the other way, no noise. And on the way home, the virbration and noise I was hearing had lessened some.

Can I put it on jack stands and test the wheel bearings by trying to wiggle the tire by holding it at 6 and 12 o'clock? If there is play, could it be bad bearings or should I go ahead and have the wheel looked at by a mechanic anyway?

Thanks for any help.

 

[00XLS]

Thats an old school way of doing it, but yeah it will tell you if their shot or not. Should be very very little movement if anyway.

 

[CDW6212R]

Rear axle bearings are caged rectangular profile steel rods, not balls. Unless they are extremely bad, there won't be an abnormal amount of play. There is normally a lot of play.
Lift the rear so that you can turn each wheel. Slowly turn each by hand while listening and feeling the area at the hub. Often you can hear or feel grinding of metal when axle bearings go bad. If they are good, there should be no grinding, but maybe just rolling sounds. Good luck,
DonW

 

[00XLS]

My bad, I thought he was talking about the front, long day.

 

[pixelflash]

Well, I want to test both front and back. Maybe I'll just take out my Haynes and jack them up on stands. Pull the wheels off and check the bearing races myself. Start eliminating things if I can.

 

[Buckshot]

Having similar issues....but I have not eliminated the front end yet. Thinking about scheduling a dyno day for two reasons.

1. The back end will get up to speed and tell me if the vibration is in the front or rear once and for all.
2. Hey, dyno numbers are always good to have....

 

[Creager]

my experince with differentials.

if its a High-pitched whirring noise it could be the Pinion bearings

if its a Low pitched noise then it could be the Carrier bearings

If it goes away or works intermittently with turning then more then likley its a wheel bearing.