4x4 not shifting

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May 25, 2020 | 08:17 PM

elange_11

Thread Starter

4wd High

Joined: May 2020

Posts: 9

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4x4 not shifting

I got a early 99 manual that I bought about a month and a half ago. I finally got around to figuring out why it was in 4H constantly. I tested the relays and in dash switch on my dad's 7.3 and they both worked. I tested the fuses and put 12v to the t-case motor and they also both worked. I did the trick with using a jumper wire on the back of the relays to switch to 2wd and that worked. I am assuming the problem is with the GEM. Everything else seems to be working fine like the auto touch windows and what not. If it is the GEM can they be repaired/refurbished. I have an uncle that does electronic repair that I would ask. Thanks!

May 25, 2020 | 10:56 PM

BWST

Got Data?

Joined: Dec 2012

Posts: 4,250

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From: Lake Stevens, WA

Hi @elange_11 and welcome. Good work eliminating several of the possible causes. I just did this troubleshooting on my 2001 F350. If the early 99 is set up the same as the later models in this area, there is some great guidance in the Tech Folder link at the top of this forum:
https://www.ford-trucks.com/forums/1...-7-3l-psd.html

Look under "Electrical" at GEM Information, and GEM wiring diagram
Also look under "Axles and Hubs" at ESOF Diagnosis 2000 MY Pt 1 and Pt 2

and in my truck maintenance thread, starting at post #10: https://www.ford-trucks.com/forums/1...de-thread.html

It might be the GEM, and it's worth taking a look to see if there is any water damage from a past leaking windshield on it. In my case, the GEM was fine, and I had to follow the pinpoint tests in the ESOF Diagnosis link to track down a broken wire.