2002 X Front End Vibrations

[ALLKINDSOFFORDS]

Usually I am pretty good at finding the strange problems, but I need some help on this one.

My 2002 Explorer XLT V-6 has a vibration in what appears to be the front end, driver's side. It starts at about 30 mph and really comes on strong at about 50 mph. Around 70 or 80 she seems to diminish, but that's probably due to a change in frequency, probably higher. The vibration is still there though. Maybe I should get a dog to sit next to me and see if he howls? Well anyway...

When I drive down the road straight, it vibrates the steering wheel and under my feet. When I cut the wheel hard right (to load the left front wheel), there is an obvious increase in vibration. When I cut the wheel hard left (to unload the left front wheel), the vibration drops off significantly. Sounds like a wheel bearing hub assy. gone bad, right. Replaced that and still had the problem. Incidentally, the hub assy. WAS bad. Very tight and rough spinning. However, the hub I replaced it with was a new SKF unit which I felt was exceptionally tight to rotate by hand. I felt that this unit had too much preload when assembled. Put that one in and had the same vibrations doing the same load/unload/straight ahead tests. I determined that the bearing was faulty and ordered two new ones from an online distributor.

I had ordered Timken bearings, but when they came in I got one Timken and one Chinese brand. Upon closer inspection I saw that the Timken had the same issues as the SKF; extremely tight to rotate. In fact, I felt what appeared to be a flat spot on the race from over preloading. Yet, when I rotated the Chinese unit, it ran smooth as butter. The way a bearing should be preloaded. I exchanged the Timken unit for another Chinese unit and installed one of the two Chinese units to replace the SKF on the driver's side. Confident I had the problem solved, I took it out for a road test and much to my disappointment, I heard HMMMMMMMMMMMMM. I did the straight/load/unload test again with the same results. Now for the question part of my post:

What the heck is wrong with this thing?????

Questions:

1) Is the front driveshaft supposed to spin even though the 4wd system is in 4wd auto? Does the driveshaft de-couple from the front differential in 4wd auto?

2) When I shift ranges from 4wd high to 4wd low, I hear the relays behind the glove box click and I can hear the transfer case changing ranges. The 4wd low then works. When I shift from 4wd auto to 4wd high, should I hear the same clicking of relays? This car is an automatic transmission. Is it possible the drive system is stuck in 4wd high? But that would still not explain the difference in the vibration under the load/straight/unload test...

3) How are the front axle shafts supported when they enter the differential housing? Are they supported on two bearings or one bearing? Do the axle shafts move in and out of the housing significantly? Is it possible that the axle shaft is whipping around?

4) How many universal joints, or CV joints are on the front axle shaft? I would assume two; one for handling the left/right turning geometry behind the wheel bearing hub assy., and one just outside of the differential housing to handle the up/down articulation of the control arms when the vehicle experiences road conditions. I have never had this apart or have seen any literature on this, it just makes sense to me that this would be the way it would work.

5) Is it possible that the axle shaft experiences such dynamic loads when I load/unload the wheel that it can cause this type of vibration?

6) Lastly, I see that the gen 3 system (splined hub assy.) looks to be fully independent of the driving system. Therefore, is it possible to remove the fron driveshaft and front axle shafts to isolate the problem from wheel bearing issues to drive system issues?

Thanks to all who can answer some or all of my questions.

-Rob

 

[trucku]

2) When I shift ranges from 4wd high to 4wd low, I hear the relays behind the glove box click and I can hear the transfer case changing ranges. The 4wd low then works. When I shift from 4wd auto to 4wd high, should I hear the same clicking of relays? This car is an automatic transmission. Is it possible the drive system is stuck in 4wd high?
-Rob

You should not hear anything when switching from 4 Auto to 4 hi.
If you were in locked in 4x4Hi your front wheels would bind up when you rolling and turn the steering. That sounds pretty bad and you will get wheel screeching or hopping.

As much as I can help.

Good Luck..
I am sure one of the seasoned guys will chime in.

 

[ALLKINDSOFFORDS]

Question #2

Thanks for your reply to question #2. I figured that this was the case. I have owned 4x4's of many different types and they all would respond with the typical binding and growling if the 4wd were engaged on dry pavement. Apparently, Explorer is no different.

 

[ALLKINDSOFFORDS]

I Found The Problem!

Apparently, the traditional load/unload test does not apply on this type of front end system. Remember, I replaced the drivers side bearing after determining that was the problem when I loaded the wheel by cutting a hard right turn (to load the left front wheel and unload the right front wheel). After the bearing replacement I did the same test and got the SAME RESULTS! Huh? Remember, when I cut a hard left turn (to unload the left wheel and load the right wheel) the noise diminished. Well, guess what? I checked the right front bearing and could not detect a problem by spinning the tire OR the rotor, so I decided to take the hub assembly off. It was then that I was able to feel that the right side bearing was ALSO no good. After replacing that one, I road tested the vehicle and LO and BEHOLD, the front end noises and vibrations are GONE! OK, so the only confusing thing is why, if the right side bearing was no good, did it quiet down when I loaded it by cutting a hard left turn and it got very loud when I unloaded it by cutting a hard right turn? Hmmmmm......

 

[ArcticGabe]

Well, unfortunately, this sounds all too familiar. Do you have part numbers for the bearings? Any advice for changing the bearings?

Thanks!!