4WD problem, Lound Thump and 4WD disengages

[Wepps10]

I am new to this site and I have a 92 Explorer Sport, I live in ND so I use my 4WD often. Last yr I was driving down the road in 4WD and then i heard a loud thump coming from underneath the front end of the vehicle. After that noise me 4WD disengaged.

At first I figured it was my manual locking hubs not working so i took them off and they looked warned out so i replaced them with some new WARN hubs. I figured that solved my problem but a couple of days later when i had it in 4WD again, the same thing happened.

Does anyone have an clue on how to solve my problem?

If anyone knows what to look for in solving this problem, I would appreciate it if the could share some info with me to fix the problem.

Thanks,

Eric

 

[MrShorty]

My BII did something similar a few years ago. Whenever I would put it in 4H or 4L, after a couple of miles it would make this big clunk. Mine would stay in 4H or 4L, but it would clunk like that every few miles. It was also difficult to get out of 4H. At the time I was running one make/model/style of 235/75/15 tire on the front and a completely different make/model/style of 235/75/15 tire on the rear. The problem went away as soon as I got a set of four matching tires. I believe my problem was having mismatched tires. The differences in the tires was enough to cause the drivetrain to bind up, and every so often, release that tension with a clunk. I'm not sure how the tension was released, whether the chain slipped or the hubs slipped or what.

Basically, if you have mismatched tires, or one tire that's low on air pressure, or something like that that would cause the front and rear to have a little bit different diameters, that would be my first thought.

 

[stang99x]

That or the chain could be stretched and jumping. That happened on a wrangler I had once.

 

[Wepps10]

Well its not the tires because i just got some new rear tires but i made sure i got the exact same kind and size as the front tires. Thanks for trying to help me out with my situation.

 

[Backin72]

Check the amount of grease in your hubs. Over-greased hubs can cause all sorts of problems.

 

[Jason94sport]

Could be a bad shift motor, 4x4 switch, drivshaft, u-joints, or X-fer case. Since the hubs are new & the tires are good, those are elminated.

 

[MrShorty]

Well its not the tires because i just got some new rear tires but i made sure i got the exact same kind and size as the front tires. Thanks for trying to help me out with my situation.

In that case, tire size differences are still near the top of my list. How much difference is there in the wear of the two sets of tires? Realize that a mere 1/10 inch difference in tread depth could mean up to 2/10 inch difference in diameter, which (if tires behaved as perfect circles) would mean about 2/3 inch difference in circumference. Or, one set of tires wants to go 2/3 inch farther with each rotation. After 300 rotations (1/4-1/2 mile depending on tire size), that amounts to one set of tires wanting to go 200 inches (or 17 feet) farther. If the tires can't slip enough, then the drivetrain has to absorb that difference.

All that to say, tire difference is still at the top of my list of possibilities. Take a tape measure (or use a string) and measure the circumference of the tires. It's better to measure the circumference directly rather than take it from the diameter. Do you have access to someone with an RBV with a good set of four matching tires you could borrow for a day as a test?

Here are a couple of articles, written for the professional technician, but still has some good information. See OTL0601 http://www.mightyautoparts.com/library/library_onthelineArchive.html
and TT116 http://www.mightyautoparts.com/library/library_techtips.html

Your call from here.

 

[Wepps10]

Alright im going to reply with the problem in detail. The 4wd dissengaged while i was accelerating. There was one thump when it happend. I would then proceed to let off the accelerator and it would lock back in and then it would be good for a little while. Like i had stated previously, i put new manual locking hubs on. The 4wd system is manual so i know its not a solenoid being funky or anything like that.

I hope that this helps.

 

[Jason94sport]

Wear difference between front & rear tires would not matter on a 1st gen X. It's a manual 4WD system not electronic. When tires get rotated they are not the same all around. Your problem may have been solved by accident by getting the same tires all around.
So now it can't be....
Tires
hubs
switch(don't have)
Shift motor(don't have)
That leaves.....
X-fer case
linkage
driveshafts
U-joints
ball joints
spindles
wheel bearings
brakes

 

[Backin72]

See if this helps.

http://www.explorerforum.com/Singleton/web/pages/fourwd.html

 

[Wepps10]

The link doesnt do me any good because i have manual locking hubs, not automatic.

 

[Wepps10]

I only hear the loud thump when in 4WD while accelerating, checked the drive shaft and everthing seams to be in tact. In 2WD and 4L the vehicle runs great with no flaws. Again this is a Manual Explorer with a manual 4WD setup with manual locking hubs. Brakes are also working well. If anyone else has had similar problems would appreciate some tips on solving this issue.

Thanks

 

[MrShorty]

The clunks are only under acceleration? U-joints are known for making clunks under acceleration.

 

[Wepps10]

How can i tell if the u-joint is bad by looking at it?

 

[Jason94sport]

Most times you can't. It's not hard to take the front drivshaft out. It's like 8 bolts. You need a 12 point socket. Forgot what size the front is, I think it's 8MM. The rear is a 12mm.

 

[MrShorty]

My limited experience:

A couple of times, I've seen bad u-joints where you could wiggle the shaft and you could see the cross wiggling inside the endcaps. That's a pretty sure sign of bad u-joints.

On my Explorer, I detected a bad wheel joint a couple of ways. Turning with the hubs locked in 2H, I could feel a wobble in the steering that wasn't there when going straight or with the hubs unlocked. When turning the shaft by hand, I could feel the joint binding up. Though, I couldn't definitively say the u-joint was the problem until I got it apart and could see how rusted the bearings were.