94 Explorer 4x4 noise

[ekafrawy]

Hi everyone,
I know there are a million posts on this as i did an extensive search, but i couldn't find one that is exactly like my problem.
When i put my 94 into 4x4(hi or lo) the system works fine. It does make a low tone whining noise when it is engaged though. I have been trying to figure this out for a while now. The wheel bearings are new, and the Auto hubs do disengage when i back up a few feet, so everything there seems normal. Its just when they are locked that I hear the noise. When i press the 4x4 button to turn off 4x4 and I keep driving the noise stays, but as soon as i back up the truck to unlock the hubs the noise goes away.
So is this a problem with the hubs or the front differential itself? Its almost as if something is rubbing lightly together that makes the noise. I'm not exactly sure how the 4x4 system works, so when i press the button to engage it what exactly happens? Does the transfer case engage the front driveshaft, which in turn locks the hubs, or does the front differential also engage somehow?

 

[DeRocha]

When you press the 4x4 button the T-case powers the front drive shaft. The front drive shaft will power the front diff which will send power to the left and right axle shafts. The rotating axle shafts will cause the front HUBS to lock. Check out the link in my sig line to see an animation of how 4x4 works. Some noise is normal, did your rig always make this noise? Driveline noise can be U-joint, or differential related. When were the U-joints, front diff fluid and Transfer case fluid last changed?

 

[ekafrawy]

DeRocha,
The fluids have been replaced about a year ago. The U-Joints have never been replaced. The truck has 98,000 miles on it, and it has been making that noise since i bought it with 60,000 miles. Do you mean the u-joints on the front driveshaft or the axleshafts?

 

[nascar_intimid]

the whirring noise you hear IMO is normal... that is the front axels turning from the hub as they are not disengaged, once disengaged the axels no longer turn and the noise goes away. It's not a loud whirring noise but you can definately hear it and also feel it in the steering and all around handling.

 

[Fixxer]

My 92' just started doing this also. Either that or I just never noticed it before.

 

[Brock94]

I notice a low whirring noise from the front differential as well. It's not really loud, but it is noticeable, and I think it is normal.

 

[ekafrawy]

so does this mean that my axles and u-joints are fine? Becasue it has recently started to vibrate the truck a little at highway speeds when in 4wd

 

[DeRocha]

It is common for the U-joints at the stub axles to wear out first (due to the greater articulation they endure). I replaced all 8 U-joints in my Explorer @ 115K Miles. The stub axles joints were the worst. They were obviously worn, rusted, and devoid of any lubricant. The other six U-joints still contained lubricant and although they were probably worn you couldn't tell just by looking.

 

[ekafrawy]

DeRocha, would replacing them make the noise to go away. I didn't have the truck when it was new, and I doubt Ford made these explorers with such and annoying sound in the 4wd system, so i think something is causeing that friction noise

 

[DeRocha]

It would be premature to suggest a particular fix would cure your noise issue as the source would need to be correctly diagnosed. The noise level on my 4dr XLT only slightly increases when I engage 4x4. You can definitely tell you're in 4x4; IMO the noise is neither loud or annoying (but each person's view is different). Since you are not the original owner it is possible the particular 4x4 driveline noise you are hearing is normal. If possible I would find someone with a 1st gen and compare the noises.