Clunk in 4 Wheel

[curlej]

I bought my Exp a couple years ago from a woman who who was selling it to get a minivan to transport her two kids (with no plans for more, her husband reported). From what I understand, she rarely, if ever, took it offroad (or used the 4 wheel drive).

That said, I have only taken it on semiserious offroad trails twice, and it has only been in 4 wheel drive in the snow other than that. The second time I took it out (a week ago), when I was going downhill in low range and 4 wheel drive, there was a serious and loud clunking sound coming from what I thought was the front suspension. I am not sure what I should suspect is the culprit. I had to take it out of 4 wheel and low range, and come down the mountain in 2 wheel drive (to be on the safe side). No noise in 2 wheel drive. Only in 4 wheel and low range.

Vehicle is a 1991, stock, slightly oversized tires, and new u-joints last year. Thanks in advance for any help.

 

[Howard]

If the surface was good grip then I think the clunck was just the front wheels unbinding from being in 4x4.
"Ford recomend that you only use 4x4 low in extremley difficult driving conditions, such as steep uphill gradients or especially difficult terrain and hauling boats from water. Note: 4x4 HIGH and LOW positions are not suitable for normal road driving."
A quote from the handbook. Ofcourse it could be something else. Does it still make any noise?

 

[curlej]

Thanks for the advice. It makes no noise in 2 wheel on regular roads. I was running downhill on a steep grade in rugged terrain. I was letting the engine slow me, so I was only braking occasionally.

 

[ahhjaws]

Is it a repeating clunking sound? Does it seem to be going into 4WD?

 

[curlej]

It was pulling fine going uphill, so I am sure it was going into 4 wheel. The clunking only happened occasionally, like when the truck would buck going over a rock or something. And it was very loud. Could it be that one or both hubs was turning itself out, then back in again? I have a manual tranny, but I have not yet switched out the auto hubs or electronic transfer.

 

[ahhjaws]

That would be my first guess. My left hub was sparatically making a popping noise for a little while, then a month later while I was in some mud. They went out completely. I lost my 4WD and it was making the repeating clunking noise.

 

[curlej]

Did you have the auto hubs that went out? Did you repair them, or did you have to replace them?

 

[94EBexplorer]

sounds to me like a blown out radius arm bushing... climb under the truck and look.... the hub will make more of a loud like clicking noise when the autos are about to blow... and they will usually buck.. for the truck is engaging and digengaging.... id check the radius arm bushings.... you can also check the hubs by taking them off.... inside at the bottom of the hub there is a little C clip that hold the clutch for the auto engage... these clips have a tendency to sheer off making the clutch slide on the axel shaft thus making it click and buck due to the clutch sliding.... engaging and disengaging the wheel.