optimus2

when it cools down does the atf return to normal levels? does it seem to do ok when cold, and get worse once yup to running temperature?

if he is in low range and it jumps out of gear he would be getting power to no wheels. i don't think it is a linkage issue. if it is a stretched chain and it was jumping would that not be a continuous and violent sound? i mean it would have to keep jumping for the front tires to never turn. right? so i would think you would hear and maybe feel every hit. correct me if i'm wrong. i'm still thinking it is a front axle issue. but i have been wrong before

what options do you have for you transfer case? 2H 4H 4L or is there a full time 4WD option? in either case if you have it in 4 low and it "jumps out" you would be in neutral and not spinning anything. if it was something in the transfer case slipping or jumping but not coming out of gear, you would hear and feel it. look into the posi lock for both adjustment and proper use. The fact that you were having problems before raises some concern but the vacuum system is know to leak and cause issues. you replaced that system, but there is a chance the new system is not set up right. If you are engaging the front axle while sitting still is asking for problems with either system. so perhaps the problem has always been proper use? again I have never used the posi lock set up. but i would engage the front axle while rolling while easing into the throttle i would keep pressure on the cable so if the splines lined up better the fork would be able to further engage. i would make sure i was really engaging as much as i could in your current set up before making adjustments.

i have not used a posi lok but it is a cable pushing and pulling a fork into place. if it is out of adjustment it might not be engaging. or if the splines are not lined up when you try to engage it, it could feel like you have pulled the cable to the end but really you have not engaged the outer shaft yet. i would play around with it to see if by moving the truck you can get it to engage further. before really putting torque to it try and be sure it is all or nothing. don't want to blow anything up trying to make it engage.

but there is no noise? a pop like something coming out a grind like something is not engaged fully to be clear, both front tires are dead. no chance the passenger side is spinning and you can't see it out your window? if i had to guess and, thats all it is, i would say your axle disconnect is not fully engaging so it will turn the tires but when under a heavier load it is pushing the fork back to the disconnected side.

so how do you know the 4wd is working? is there any noise when this starts happening? do the front tires seem to jump at all as if trying to go? are you rolling when you engage your front axle? by this i am getting at is there a chance the fork is not lining up when you try so it is never really engaged?

thanks for taking the time to measure. ended up going a different route as simpler options came available. found a drive shaft out of a lwb mj with a dana 35 so i gained 1" there. and a yoke from a different mj (I don't know the year) that was 1/4-3/8" longer than mine. combined the 2 made up the extra length to return me to a safe engagement at the transfer case.

can get the parts for cheap, don't have the parts on hand. wanna make sure its worth it before i go after it. thanks for the help

After doing my SOA lift I am at about 7" of lift and no longer comfortable with the amount of engagement I have between the rear drive shaft and the transfer case. It still drives and there are no vibes, but I don't trust getting into a situation where i would be looking for a lot of torque. do to my being cheap and low on funds I am trying to avoid building a new rear drive shaft. I have been told that swapping the tail shaft portion of a tj transfer-case onto mine would add to the over all length(don't know how much yet). This would solve my short drive shaft problem and would be an internal oil seal transfer case instead of the external that is currently in place. This is an option to me because I can have the parts required to do the swap for cheap/free. tail housing, output shaft, slip yoke that would match question is can anyone confirm this? Has anyone done this before? Still researching this on my own as well but if someone can give a strait answer maybe it would save me some hassle.

coil on its way out? an xj I used to run had this problem, would start and run fine till it was hot, then a hard start and would not run good till it seemed to clear itself out and burn off extra fuel. coil was getting heat soaked. and was not making the contact it needed to, so it was a weak spark/no spark. new coil was instant fix. Not sure this is the case for you, but might be worth considering.

my 1990 with a 44 has no bulge. so maybe the change was in 91? or later 90?

no personal experience, but in reading about it before I have seen complaints that people get a lot of water problems going this way.