Np242 jeeps bucking above ~35 mph

[xcm]

PROBLEM:
Ax15/np242 jeep was bucking at 40-50mph, distinctly NOT an engine hiccup/stutter or fuel problems. Jeep sat for years, had transmission rebuilt, transfer case PASS'ed an external OPcheck, fluid full of fork pad pastic and shards of cast iron(?) Felt like, and everyone else assumed was a trans problem when asked.

SOLUTION:
Np242 mode shift fork severly worn, allowing the collar it rides on twisting, engaging 4x4 (or low range, it doesnt matter which). After tracking down a replacement fork, it becomes obvious this is a known issue, see pic of three shift forks with identical wear. You also have to completely take the t/case apart, as the worn face points down, and cannot be seen until both shift forks are removed....

PICS:

 

[ehall]

Its interesting what you run across. I've had several 242s apart, none were missing any of the pads, but all of them have damaged differentials.

 

[xcm]

My guess is east coast jeep 242's probably see a lot more time in fulltime 4wd than cali jeep 242's, hence the wear on the diff section? When i went looking for a replacement, i had 4 np242 mode shift forks in my hands.... 3 were damaged identically, the fourth was what i put back in it.

Id love to see pictures of the problems you have ran into ehall (or at least a description so i know what to look for, in the future)

The upper most shift fork had pristine pads...

 

[ehall]

Only have pics of a couple. This one turned blue after a thrust bearing shattered

This one the sun gear welded itself to the shell and scratched a channel into the housing

The one I have installed now has a little extra slop. The differential tends to pick up gunk and then when you clean it up there is suddenly excess movement.

I love the cases, but I am starting to hate the diffs