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HELP! NP231 Range Fork Keeps Wearing

CHGreen01

NAXJA Forum User
Location
Atlanta
0AKk62y


Has anyone ever experienced this problem? The range fork in my NP231 keeps wearing away and allowing the collar to jump between 2wd and neutral. It has happened twice now. Everything else inside the transfer case seems to be fine. None of the bearings are loose or worn, the shift selector and mode fork all look good. The main shaft is good and tight when everything is assembled. I'm stumped at what it could be causing the problem.

Background: About a month after I bought the jeep I installed an SYE kit. The fork gave out about 2,000 miles after the sye install. I figured I had messed something up with that or maybe the plastic pads on the fork had just worn away over time since the case had almost 200k miles on it. I cleaned up all the parts real good and replaced the range fork with a new one from Quadratec. That one lasted about 5,000 miles before I experienced the same problem. I did not have the shift linkage hooked up and I'm also not running a front driveshaft. Just 2wd all the time on the road. I have a double cardan shaft in the back with good angles, absolutely no vibrations in the Jeep at all. 1995 Cherokee Sport, 4.0, AW4, 5" lift, 32" tires, Rough Trail sye from Adam's Driveshaft.

Could the oil pump be bad? Whats a good way to check the pump?
Thanks
 
That makes sense, I guess the steel mode fork rod could wear away at the boss in the bottom of case with some heavy/extensive shifting over time. I do have another transfer case from a 92xj and the mode fork rod is much tighter in that one. It's a lot more difficult to re-install than in my old case. So maybe that is the problem. I'm planning to swap my SYE parts over to the 92 231 and put it in the Jeep. Hopefully I won't have to deal with this again.
 
The other thing could be that the linkage is not adjusted correctly, causing a constant force on the fork.
 
Per the installation instructions on the Adam's driveshaft page did you measure how much the shift rod protrudes from the case? Some need to be trimmed a half inch.
 
Per the installation instructions on the Adam's driveshaft page did you measure how much the shift rod protrudes from the case? Some need to be trimmed a half inch.

The original 95 transfer case had the shorter shift rod. So I didn't have to trim it. However, this new 92 case I have did have the longer rod that I had to trim. Also I always had it in 2wd so the rod wouldn't have been sticking out all the way in either case. I've got the new T/C in the Jeep now. So far so good
 
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