I seem to see this problem posted a lot, but no clear solution. I have a 97 F150 4x4, 5.4L Auto, with electronic dash switch. Had it hauling snowmobiles a couple of weeks ago when I discovered that the 4x4 wouldn't engage. Bad times. Dash light would come on, but no power to the fronts. Checked fuses, both OK. I noticed later that the '4x4' and 'low' lights stayed on, despite the switch on '2 Hi'. Went off a short time later and drove it home fine in 2wd.

Got her home and started checking different things after checking the web. First stop was the vacuum solenoids. Had power to one on '2 Hi' position, power to the other on '4 Hi'. That seemed right. About that time, I noticed that I could hear the engagement 'click' to 4 Hi and the 'chunk' to 4 Lo. Cool, must have fixed itself. That only lasted a couple of tries, then nothing. It was replaced by 5-6 clicks behind the dash whenever I start the engine, regardless of the switch position. Decided to take it for a test drive and realized CRAP!, it's feels like it's stuck in low. Doesn't feel like the front drive is engaged because the steering doesn't shutter on hard turn. I can get it to manually shift into 2nd, but it still feels like it's in low. Won't go over 15 mph without revving engine. Start the engine, shift to neutral, still won't disengage. Crawled underneath and tapped on the electric motor while my son switched through '2 Hi', '4 Hi', and '4 Lo". No change. Disconnected plug to electric motor and using a test light, discovered I'm not getting power to any terminal, despite which switch position it was in. Shouldn't there be power at some point? Checked the vacuum solenoids and realized that both power connector had a hot connector, despite switch position. (Used a meter when I originally checked them, so I don't know if they normally have power to the connector and activate through the ground. Didn't check them again with the meter.)

I've found a lot of similar problems posted, and a few possible solutions, but none seem to fit the same group of problems. Thought it might be the motor, but how could that be if there's no power to it. Even if the solenoids have correct power and no leaks, that only effects the front drive engagement, not the Hi or Lo engagement, right? The GEM module gave me some problems when I first bought the truck because of a leaky windshield, but that went away when I had the windshield replaced, over a year ago. Besides, none of the other issues I had with the GEM issue appeared this time.

At this point I'm stumped. Chilton manual is worthless. Pride won't let me take it to a shop. Can anyone think of something I might have missed and what to do to troubleshoot it? Any help would be appreciated.

 

Quick update. Checked the wiring connectors to the vacuum solenoids again with the voltmeter. Driver's side solenoid has constant 12V across the terminals, engine off or on, no matter which switch position. Passenger's side solenoid has a low current (1-2 volts) constant across the terminals, despite engine and switch position. If chilton manual had a wiring diagram for the 4x4 system, I might be able to figure something out, but it doesn't. Waste of money....

 

dont know if this will help or not but on a 99 ranger i had the 4x4 would play tricks on me like that, sometimes wouldnt engage and sometimes wouldnt disengage, then it just quit all together. Dash lights would come on but no 4x4. Took it to the stealership and it was that electronic shift **** that mounts to the transfer case (dont know the name of it) bought a new one for $219, 3 bolts and one wire clip later it was back up and running.

 

wow, oops again

 

Both white/light blue stripe wires should have 12V in run. The GEM will ground the left side (closest to engine) solenoid to disengage the front axle. It will ground the the right side solenoid (closest to fender) to engage the front axle. If the GEM doesn't see Neutral it will not let the truck come out of 4Lo. If the GEM had water leaking on it it may well be the root of the problem. The shift motor only has power when the GEM sends it a signal to move the shift lever. Once the shift is completed the motor shuts off. There are 2 wires that control the shift motor. A yellow and an orange. The GEM alternates between 12v and Ground to these wires to control which way the motor turns. The GEM uses the transfer case shift relay module to control the power to the motor. There are contact plates inside the shift motor assembly that indicate the position that the shift lever is in. This is what the GEM used to know what the T-case is doing. Any one of these components can fail.

JMC

 

oops double post

 

Alright!! Now I have something to work with. So I'm assuming that if I disconnect the harness from the shift motor and use a test light on the yellow or orange wire connector, I should get some sort of electrical signal when the switch is operated, right? As for the solenoid connectors, each has one hot wire, but only the left side solenoid connector has 12v across the terminals, and that's full time, regardless of switch position.

Was hoping it wasn't the GEM module, since none of the other glitches from the last time have appeared, but who knows, maybe this is the only component effected. Sure seems like a lots of things are pointing to it. Is it possible to eliminate the switch as the cause by removing the switch and jumping the proper connectors on the harness plug? If so, do you know which wires (colors) are the power and the '2Hi' & '4Hi' leads?

Thanks.

 

yes


Both solenoid white with blue striped wires have 12 volts when in RUN. In 4x2 you will have voltage across terminals on the solenoid that is nearest to the engine. The GEM grounds the solenoid to unlock the hub and maintains vacuum till you shift into 4x4. If you have voltage across any of the terminals all the time then the ground is shorted to ground.

The GEM runs the motor. So lets say you want to go from 2Hi to 4Hi. The GEM turns the motor on and runs it say clockwise. The GEM keeps power to the motor till the contacts that indicate 4Hi are touching and then the GEM turns off the Motor. I am sure something could be rigged but in the long run it would be better to fix the existing problem.


JMC

 

I changed out the GEM module, but the problem still exists. The switch checked out OK with the ohm meter, with all readings within specs. Unfortunately, all the new GEM did was move the transfer case back into 4Lo. Gonna have to crawl back under, pull the shift motor, and manually shift it back into 2Hi. The last time I had to do this, I was able to move the slot on the motor to align with the shift **** on the transfer case by applying power to the orange and yellow wire connectors on the motor. Would this eliminate the motor as the problem?

The only other possible problem source I can see would be the transfer case shift relay module. It appears that it's located in the dash, which would coincide with the 5 clicks that I'm hearing when I try the switch. I pulled the oval panel off the top of the dash, but could not see it through the opening. Is there a trick to getting to it? If it's one of those impossible to reach parts, is there a way to test it from other connector points? Does Ford have a tester that will narrow it down to the correct component?

 

When the motor turns it turns the Shift shaft and moves clockwise and counterclockwise accordingly. The contact plates in the shift motor assembly open and close the circuits that tell the GEM where the shift shaft is. The motor could well be working but the contacts are not telling the GEM where the shift shaft is. If the GEM doesn't know where the shift shaft is it cannot shift. As the contacts are integral to the shift motor. The shift relay is controlled by the GEM. Based on where the shift shaft is perceived to be the GEM Grounds the relay to vary the polarity of the shift motor to turn it. If the GEM doesn't know where the shift shaft is it will not shift the t-case. While the Shift motor is out try turning the **** on the dash to 4Hi - 4Lo and back again to see if the motor works. If it doesn't I would suspect the contact plates. If you have access to a scanner look for any DTCs.

JMC

 

OK, since I had to pull the shift motor to manually shift into 2Hi, I had my kid move the switch while I held the motor. I could feel the motor jerk, but not turn. Later, with the motor removed, I was able to apply power to the orange & yellow connectors and was able to get it to turn from one stop point to the other. Seems that the motor is ok, so now thinking that the contact points inside the motor could be goobered up. Just need to find the special torx head for the screws.

To keep my run of "things that could go wrong" intact, I ran into a problem trying to remove the motor, due to a brown wire running from the connector block to the transfer case. There was no way to disconnect it from either, so I just cut the wire and will splice it back together when I install the motor. What does that wire run to, and is there a correct way to disconnect it?

 

The brown wire is for the electromagnetic clutch. It spins the front driveshaft up to speed so the front axle can lock up without grinding. The procedure is to remove the pin from the connector. When you replace the shift motor you reinstall the pin in the new motor's connector. Ford only sells a complete motor assembly. So if you cannot get the contacts sorted out you will need a new one.

JMC

 

MY 4x4 wont engage front wheeles. I have the manual shift lever. Do I still have electric motors like the electric shifter trucks and expis.All the shift linkages , drive shafts seem normal. I thought the manual shift would be all mechanical like my 78 f150. My1998 expi has the dash shifter. I just bought this truck and am trying to get every thing working. Thanks for help on this.

 

The manual SOTF t-case only has an electromagnetic clutch. No electric shift motors at all. The front axle disconnects using a a vacuum motor to push/pull as shift lever that is attached to a shift fork in the axle. The shift fork slides a splined collar over the splines on the passenger side axle to engage/disengage. Your 98 EXPY has a different clutch. It has a clutch pack to allow the front wheels to slip around corners when in 4AWD. Anyways if your front wheels are not turning it could be internal to the t-case or a problem with the front axle lock up system. 1st jack up the front wheels off the ground and place the tranny in P and the t-case in 4Hi. Try to turn the front drive shaft. If it doesn't turn the t-case is OK and the front axle engagement needs to be diagnosed. In most cases the t-case is fine.

Regards

Jean Marc Chartier

PS. I would start another thread so this one doesn't get confusing.

 

Just would like to know how much for this part. I have a 98 f-150 that i took in to the dealership and was quoted around $ 700.00 to fix my broken 4x4. $500.00 for Gem module and maybe $ 200.00 for a fuse panel. Also if i can get the part how hard to change it.