check for any scratches on surface the roller make contact with or any scratches on the rollers themselves, one bad roller can make it hard to engage. Also make sure you are using the right fluid in the diff, this can also create problems. Is the coil sitting at the right distance in the casing, per the service manual if this has shifted the magnetic current maynot be sufficent to slow the armeture enough.

 

Maybe this will help

Brian

 

Mine was doing this very same thing. After the fourth time of taking it apart, I got it. I replaced the armature plate. The wear marks looked as they should have so I always thought it was ok. After looking very close at it, and laying it on a very flat surface, i noticed slight warpage. It was not much but it must not take much. I was like you. Had tried everything. I don't believe in just swapping out parts so I always try to test and check them before I buy. If you are still having problems and you have done all the tests, try the armature plate. My 4wd has not worked this good since the day I bought it. I love it again! (was starting to hate it.....

 

X2 This is what I was also thinking could be the problem.