4WD Problem not fixed yet--

[RoadrunninRN]

Hubby has checked and cleaned auto hubs, and just yesterday took the shift motor off and checked it all out. Still no luck. The 4WD still disengages at will, and makes horrific THUMPS, GRINDS, CLANKS, etc, as if it is going to leave parts all over the road!! Hubby did notice yesterday that in coming up our snow covered hill, that if he went very slow, not putting the 4WD under any "pressure" it seemed to stay in, at least long enough for him to get up the hill and back to the house. He talked with a mechanic friend last night, who told him that his best guess was that the shift motor is bad, because he sees alot of that in Ford Explorers.

Now--my Exp is a 91, however, up until I moved here in 2001, the 4WD was very rarely used, so I find it hard to believe that the shift motor is wore out in just 3 years time, especially when I can probably count that the 4WD has been engaged less than 50 times in those 3 years.

Is there a way to accurately diagnose that? And in the event it is "bad" --does anyone know if the shift motor on a 1989 Bronco 2 might fit my early 1991 Explorer. Hubby has a 89 Bronco 2 that he had junked a few years ago due to other probs, and he is wondering if the 4WD parts may cross over. (If the wind was not gusting to 60mph here with the wind chill well below zero--he wouldn't be asking, he'd be taking the Bronco apart to find out!) Anyone has any suggestions or knows if this will work-- we'd like to hear from you....

As always-- thanks for the help! Hubby is great with vehicle repairs-- but this has him stumped!!

 

[MrShorty]

What do you mean by "disengages at will" Is it popping from 4H to 2H and you have to push the button to go back into 4H? Will it stay in 4L? If this best describes the problem ,check the position sensor in the shift motor. Maybe try leaving the shift motor off and shifting by hand, so you know the shift motor isn't doing anything weird.
Or is the 4WD engaging/disengaging on it's own, kind of like a chain slipping? This behavior could indicate the chain in the transfer case has stretched, in which case you need a new chain/transfer case.