I have a 89 Comanche (used hard by previous owners, trying to rehabilitate the old work horse) with an inline 6 and an AW4.  Like an older 2006 post it seems to slip out of gear.   Never when accelerating tho.   Seems to be when I am trying to maintain speed or just coasting along.  

The 2006 thread petered out without any followup so I was wondering if anyone can give me some insight?  Thanks!  

could be a cracked servo/rings, or stuck valve, droping the line presure.

it is full and was checked while hot and running?  

It was full and the behaviour seems to be worse when it is at full running temperature.  

I am having a tranny guy do a road test tomorrow.   It should be interesting.   I don't know anyone in this area to get references from, but he seemed to be willing to explore little stuff first rather than assuming it was a bad tranny.

It slips out when at cruising speed.  As soon as I apply gas to the engine it slips back in.   Makes me wonder if some of the posts in various places about the throttle position sensor might be the problem.  

The road test ended with this result.  

The tranny guy adjusted the ident cable (?)<no charge, for that alone I would recommend them> and looked over the truck.   He said the transmission needs service but probably is not the problem.   He thinks it is slipping to/from lockup and overdrive.

He suggested, since I am busted broke, that I go through the electrical since in his experiance these jeeps are notorious for ground problems.

The guy I bought it from was a hack.  The battery is the wrong size, in really bad shape and the cables show internal corrosion.  Also, there is a lamp wire with the click wheel switch under the dash going to a relay.  The wire does not connect to anything else!  

The tranny guy said if it is still causing problems after I go after the electrical to bring it back, but he seems pretty sure it is not the mechanical aspect of the transmission.  

Well, looks like I was too optimistic.   The adjustment has not helped over much.  It still tends to shift erraticaly at speed, but is fine when accelerating.

I think I will try to go through as much of the electrical as possible this weekend.   Maybe pull some of the sensors and make sure the connecters are clean.  

Looks like I will be investing in a multi meter next month...  

On a side note it went through DEQ check in Oregon with flying colors after sitting for about 9 months.   All I did before running it through was change the oil, oil filter, air filter and serpentine belt.  

Well, went through as much of the electrical as I could this weekend.   Took out a lot of garbage.   That strange wire was a rather ingenius ignition interrupt to prevent theft I suppose.  Just poorly executed.   I did not replace the batter but cleaned the posts and check the cables.  Everything seems fine.   Still shifts erratically at speed.  

dang. theres a tranny shop on 77th and sandy blvd, I used to work there, it has a different owner now,
jerry's transmissions, they may be able to help out there also.