CHGreen01

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

tech

Check the oil passages to make sure they are not plugged the pump could be trying to move the oil but if the passages are plugged it will burn up something and what oil are you using ? and make sure the ranged slide and gear are not twisted because it will put pressure against the shift fork .

chevmec1

Looks like excessive heat on the shift forks possible lubrication problems, something bent?

CHGreen01

I've been running Dex-merc III in the transfer case, same as the AW4. I think the problem may be coming from the mode fork rod. It doesn't seem to be bent but I think it has worn away the boss that it sits in in the bottom of the case. When I assemble both the forks into the case it slides in very easily with almost no effort. I have another NP231 from a 92 XJ and that one is much tighter and difficult to install. It has to be aligned perfectly to fit together. So I think the little bit of extra play is allowing the range fork to hang lower and rub against the collar as it spins. I've got the SYE swapped over to this other T/C now so I'm going to put it in the Jeep and see how it goes. Hopefully no more issues.

chevmec1

With the same repeat failure something is wrong either worn or bent, nothing lasts forever good luck!