So I was having intermittent engaging of my 4x4 on my 97 5.4. I had to replace the windshield, and the installer told me that there was rust along the edge that he fixed. Knowing that was one of the major contributors that cause the GEM to fail, I replaced it with a new one from Ford (referenced from my VIN). In still getting the same intermittent 4x4. Any ideas of what to check next? I am thinking about the TC relay module, or to physically replace the relays under the oval. I can hear a very faint click of the relay that can only be heard with the oval off when trying to switch into 4H. I don't try to switch it into 4L as it has remained stuck in 4H for a couple days before, and at least I can disengage the vacuum lines and roll around in 4H if needed. I really would like to resolve this without going to the dealer for them to run their diagnostics to the GEM and stuff. Thanks for the assist

 

If it goes into 4H it tells you the front actuator is working and the Transfer case motor is running to the first position and stopping.
You apparently have a reverse operation issue.
Check the fuse seating, the harness plug up at the case motor if the motor is not reversing.
After that take the motor down and inspect inside for a cause affecting reverse operation. It is a DC motor so the polarity is reversed by relay to make it return to normal 2wd position.
You can test it's operation while you have it free from the case.
Good luck.

 

Okay, sorry for the delay in the reply, but I'm in school, and Calculus II was kicking my ***, and I kind of let this fall through the cracks. Anyrate, let me re-state the problem, as I do not think that I was thoroughly clear when I first described my symptoms.

The truck will go into 4H and even 4L-On occasion, that is maybe 1 of about 100 attempts. I have given up on trying to engage the 4L due to having the same 1 out of 100 chances for it go switch back to 2WD from 4-It's a lot easier to simply release the hubs and roll like that for a bit, than to have to get the transfer case back into a high gear.

On the rare occasion that the truck decided to switch, I get all the clicks from the relays doing their thing under the oval. (I'm actually debating changing all the relays there for good measure). I am wondering about the possibility of the transfer case relay control module being faulty?

Back to the history of the problem, I changed the GEM module with a new one from Ford, matched to my VIN, of course. I did this since when I had my front window replaced, it was stated that there was a lot of rust indicating a leaky windshield. Switching the GEM did not change the symptoms of the problem at all. I'd really like to get this issue resolved without having to roll into the dealership or having to spend significant money. Actually, I rarely used the 4X4 even when it was available, though for me it's more about a function on my truck that is not working properly, and that just flags my OCD receptors.

What I've also checked: Switch, the resistance in each of the modes is correct per the Ford repair manual (I have the DVD). I actually have 2 selector switches, and the resistance is identical on each one (mode to mode). I started doing the 4X4 test per the manual, but that quickly ended when I got to test 2 or 3 which requires the Ford tester, that which I do not have, and at cost of $1500, I may never have.

Thank you for all the valuable input, I will try to respond quicker in the future.

 

Check the vacuum switches behind the battery on the firewall. Easy to find, look for at least 4 vacuum lines and 2 electric plugs. There's one to lock in the front end, one to release. If they don't release the front end, could make it hard for the transfer case to release.

Check to make sure vacuum is present to each (will need a $20 vacuum gauge) and then check to make sure they switch and send vacuum to the front end. They catch water and can stick or freeze and break. I had a bad one not moving at all and the other would only send 10" of vacuum to the actuator. If the switches are good, check to make sure the actuator on the front axle is moving.