Acting on the replies to my post "AUTO TRANS SHOT?", I'm 90% sure the problem is a false neutral condition in the transfer case.
The difficulty now is that after getting under the car a number of times with the 9/16 wrench to move 2WD/4WD lever it won't stay there and goes back into the false neutral condition .
The question is how to keep the transfer case from going back into a false neutral?
Mine wasn't trying to jump back, but at one point I wired the lever back to make sure it stayed put. I twisted 2 or 3 wires together to make something like a cable and tied it back to something - not sure what.
I wonder if maybe you should try to find out why it won't stay put in case there is
a chance of damaging something if you force it.
There may be a problem with your vacuum shift motor or the vacuum source to the port that supplies vacuum for 2wd. You would need a vacuum pump to test the 2 ports of the shift motor that is located on the side of the transfer case and see if they hold vacuum. Then proceed from there. But you can wire it into 2wd or 4wd until you get it figured out.
I have a vacuum pump.
I don't see anything in the M.R. 251 regarding the vac lines going to and from the TC. Would be nice to have a diagram of those lines indicating colors.
I need 4WD so will try to wire it there - seems harder to move the lever to 4WD than to 2WD; also determining how far the lever should move to engage.
This from a 229 in a Jeep. It may be similar to the Eagle.
(http://frontier.net/~mystkblu/88np229vacuumcontrols.gif)
Would you know the source of that vacuum on a 258; and where the storage tank is?
Is there a mechanical downside to wiring the TC lever in the 4WD position?
The AMC Eagle was designed to be All Wheel Drive. There is no downside to wiring it into 4WD permaneantly. I personally have never driven an Eagle in 2WD without mechanical damage. I never will own an Eagle without eliminating the vacuum system. It is considerably more trouble than it is worth.
I've gotten a consistant 29 miles per gallon out of my stickshift 258 SX4 while wired into 4WD, I do not agree there is an appreciable difference in fuel mileage. You'll never know its in AWD until it saves your butt.