1997 F150 4x4 issues
 

Hello, it has been a while since I have been on this forum as I had sold my last Ford. Well, I recently bought a 97 f150 lariat 4x4 with the 4.6l for a weekend driver. P.O. had told me a new transfer case shift motor was installed, and it does look like a new part under there. Night I bought it everything was okay, until I took it to the car wash. About an hour after the car wash it engaged itself into 4x4 and I could not get it out. Messed with the switch on the dash a bit, and nothing. No lights come on in the dash either. Suddenly disengaged itself. After I shut it off to go into the store, I come back out, turn it on, and find it has engaged itself again, still no dash lights. I then replaced both iwe solenoids. Currently, the dash switch will not lock or unlock the hubs, but if I swap vacuum lines at the actuator, it will move the arm to lock and unlock the hubs. When I turn the switch, I hear no clicking whatsoever, and no dash lights. Also, I don't know if this is related, but while accelerating it feels like I get a high rev from 1st to 2nd, and when it's supposed to shift to 3rd, it will rev up to 3k rpm and will start violently bucking, like it's trying to shift but won't. I can't get it past 35mph. If anyone has any insight I would appreciate it. I was trying to find my symptoms but I was not successful. Sorry for the long post, I'm just trying to be as detailed as possible.

inspect the two solenoids on the firewall by the battery.
look very closely for a vacuum leak. there is also a reservoir in the right front fender.
I have some pics of the vacuum components in my gallery here.

Appreciate the response! I had replaced them upon inspection due to one missing a cap and being corroded. It did not fix my problem. Vacuum is good as well.

arrgh…..well now check all electrical connections

From what I have looked at already power to the solenoids is not being switched from one solenoid to the other when the switch is moved to any position. Just stays at the one solenoid. Someone told me the culprit was most likely the GEM module, but as it is difficult to get at, and difficult to find the right one, I wanted to exhaust other options before I tear it out.

Must have a leaky windshield and the GEM got wet after going through the carwash.

That's what I thought, but I figured guys on this forum would know better than me

so do you see any moisture by the GEM?
or, is the switch bad?

I saw no moisture by the GEM, and I thought for sure I would have being as we have had a considerable amount of rain around here lately. I also ohmed the switch on the dash and it tested good.

Also, would someone be able to guide me to where I could get a new GEM module? I saw somewhere there were only a couple different types of GEM modules for these trucks, and I found one on o'reilly that had the options my truck has and the description said it was "pre-programmed" or would I be better off at a yard?