97 Eddie sohc 4.0 4wd stuck in 4 wheel drive

[tcross8361]

Ok, I posted this problem in the wrong section before so I'll try it again. My explorer is stuck in 4H. I unbolted and unplugged the transfer case motor and ran a jumper to the battery. The motor was working fine. So I plugged it back into its wiring harness and when I turned The ignition back on the motor turned back to the 4H position. I left it unbolted from the transfer case and went through the 4 wheel drive ranges using the dash switch and it did nothing. So My conclusion was it was a switch problem or in the wiring some where. I also checked the number 4 mini fuse under the hood and the number 26 on the side of the dash, they are both good. So where do I go from here? Is there any relays tied in with the 4 wheel drive system that I don't know about? I really don't think it is an internal transfer case problem at least till I get the switch working. But I don't know much about these explorers. I've only owned it 7 mos and its my first one. My last was an 89 ranger. I tell you I really went against my better judgement buying an electronic 4wd. so, if anyone can help I sure would apprieciate it.

 

[tcross8361]

ok, I have an update. It's not in the switch. I went out and tryed somethineg my neighbor suggested. I put it in nuetral and it went into 4low and back to 4 high. But only when it is in neutral. The reason why i think it is stuck in 4wd is cause when it in park and I jacked it up the front wheels don't turn, only in nuetral. I guess maybe I should do it with it in drive.

UPDATE: Ok I tryed it in drive and it is still grabbing. As near as I can tell it is in 4H. So, Any suggestions?

 

[dogfriend]

Your post is somewhat confusing to me, but I think that you may have some misconception about how the 4wd works. I also think you might have a problem, but I'm not sure - it may be working the way it is supposed to.

First a short summary of how the Control Trac system is supposed to work:

The front and rear driveshafts are always turning when the truck is in motion. The rear shaft is always powered thru the transfer case. The front shaft is only powered when the electromagnetic clutch inside the transfer case has power. Power for the t-case clutch is sent by a TOD solid state relay behind the dash. The TOD relay turns the t-case clutch on and off when it receives a signal from the GEM (General Electronic Module - a computer which controls door locks, intermittent wipers, and 4x4 engagement). The GEM decides to turn the t-case clutch on and off based upon the position of the 4x4 switch and a couple of other sensors including front and rear driveshaft speed sensors.

In 4x4 Auto, the GEM only sends a short duration PWM (pulse width modulated - a signal which the amount of power is controlled by varying the length (in time) of the pulse) signal to the t-case clutch under normal conditions. If the GEM "sees" that the rear driveshaft is turning faster than the front shaft, it interprets this as rear wheel slip and increases the PWM signal to the t-case clutch which sends more torque to the front wheels. The GEM continuously monitors the speed of the front and rear driveshafts to decide how much torque to send to the front wheels in 4x4 auto.

In 4x4 High, the GEM sends a higher level PWM signal to the t-case clutch to send a certain amount of torque to the front all of the time.

In 4x4 Low, the shift motor moves to engage low range, also the TOD relay is bypassed to send power to the t-case clutch continuously. The GEM will not allow the t-case to shift to low range unless the transmission is in Neutral (and the truck is stopped - or moving less than 5 (or 3?) mph.) Also, the GEM will not shift back to high range unless the trans is in Neutral.


So, back to your issues - I think that your shift motor is operating properly - it is only supposed to shift when the transmission is in Neutral - this is what your truck is doing.

Your truck is always in 4wd - but it should not "bind" when in 4wd Auto. If this is the problem, then it may be a problem with the GEM or it may be a problem with one or both driveshaft speed sensors. Some people have reported success with cleaning the speed sensors. If you search for "speed sensors" you should find some more info.

 

[tcross8361]

ok, thanks for the tips. See I've read some threads on these sensors but I'm not sure where they are located. And I've also read stuff on the tod relay and the gem, again not sure of there locations. Big thanks though you've given me a new avenue of aproach here.

 

[dogfriend]

The driveshaft speed sensors are both located at the rear of the transfer case. You can find them by tracing the wires from the connector that is closest to the shift motor. Besides the wires for the shift motor, you should have 5 other wires - 2 sets which go to the front and rear speed sensors and 1 larger brown wire which goes to the electromagnetic clutch inside the transfer case.

 

[tcross8361]

AHHH the infimous "brown wire mod" wire huh. Ok, I thought those might be the ones. I noticed those when I was unbolting the motor. Hey quick question, The bolts I took off the tcase motor looked like they had some sort of lock tight or thread sealer on them and the motor had some type of silicone gasket material around it where it mated up to the tcase. Is it important to put this stuff back on there when rebolting it up? Greatinfo man thanks for sharing it with me. I love this forum.

 

[gijoecam]

Dogfriend summed it up pretty well. I also replied to your PM too....

Basically, by disconnecting the brown wire from the transfer case, either by unplugging the proper plug (NOT the motor) or by installing a switch in the brown wire, you interrupt the power supply to the clutch coil that engages the front driveshaft. If interrupting the power to the clutch doesn't allow it to disengage, then, yes, the transfer case will need to come out for a clutch replacement.

However, I'm still not clear on what the problem is you're experiencing?

The reason why i think it is stuck in 4wd is cause when it in park and I jacked it up the front wheels don't turn, only in nuetral. I guess maybe I should do it with it in drive.

What do you mean by "they don't turn"?

-Joe

 

[dogfriend]

AHHH the infimous "brown wire mod" wire huh. Ok, I thought those might be the ones. I noticed those when I was unbolting the motor. Hey quick question, The bolts I took off the tcase motor looked like they had some sort of lock tight or thread sealer on them and the motor had some type of silicone gasket material around it where it mated up to the tcase. Is it important to put this stuff back on there when rebolting it up? Greatinfo man thanks for sharing it with me. I love this forum.

I believe that the purpose of the silicone sealant is to prevent water from entering the transfer case by getting into the opening for the shaft which shifts the t-case from high to low range. I think it is important to replace it, especially if you plan on making any stream crossings.


The brown wire is the same "brown" wire as in the "brown wire mod" but most people add a switch or relay inside the cab, so you need to trace this wire back. A popular location is under the drivers seat, before the wire goes thru the floor. Other locations are behind the dash or in the drivers side kick panel.

 

[tcross8361]

well the problem first accoured when I thought I had a brake caliper problem cause I could smell burning brakes. Well I located the smell in the front left wheel and no others. So I figured I had a caliper sticking, so I jacked the front left up and pulled the tire off to inspect the caliper and pads. I tried turning the wheel and it wouldn't turn freelyin park. So, in my limited experience with these things, that tells me the 4wd is engaged. Now keep in mind like I said before, I'm very new to this control trac and electronic 4wd stuff. My old 89 ranger (my vehicle before the explorer) was all manual hubs and shifter, the front wheels turned freely on it until you engaged 4wd. My cousin's husband was a mechanic at the local ford dealership. He was the first one I called with the problem. He didn't think there was a problem but he put his disclaimer on it saying "he wasn't a tranny or 4wd specialist". So maybe it isn't all that I think it is but if it is stuck in 4wd I want to address it cause I don't want to tear up my tranny or something else in the drivetrain. I do want to say thanks to you guys for the helpfull insight on all this stuff. I wish I would of found this forum earlier.

 

[gijoecam]

OK, simple check.... Jack the front end up with the key off and try and turn the front driveshaft. You may need a good pair of channel-locks to get it to turn initially, especially if the front brake or wheel bearing is giving you fits (more on that in a minute). If the front driveshaft will turn one full revolution, the transfer case is NOT locked-up. Also, if the transfer case was locked in 4 high, there would be other tell-tale signs.... binding noises and/or hopping when turning in a tight circle as the driveline binds-up.

If the brake or wheel bearing on one side is dragging excessively, when you jack the front end in the air, the front driveshaft will try to drive the "free" wheel twice as fast as normal. (like when you spin one rear wheel of an open diff). In general, if the front driveshaft will go more than a single revolution, it's free enough that it's fine.

The root of your problem could still be a brake caliper frozen-up or a bad wheel bearing causing the heat.... or have you ruled them out in another way?

-Joe

 

[tcross8361]

No, Haven't ruled them out yet. I was actually told that brake problem might be a bad brake line too. But that was the auto zone sales man. So, I might while I'm at it just replace calipers pads on both sides. Test it and maybe try the front left brake line. What the hell i'm on vacation for a couple weeks, so I've got the time and that is relatively cheap to do. And if I do that then I'll at least have warrantied brake parts on it as the parts that are on there now aren't. Also I do know my ball joints are starting to go bad. I've got the parts in and my neighbor gonna help me with them next week.

As for the 4wd issue. I crawled under it this morning and made sure the gear oil is topped off (pretty dark, may need flushed and changed). I siliconed that tcase motor up And was checking the brown wire location and the speed sensors (that dogfriend was telling me about). And in doing so I found some sort of vacum line on the front end side of the tcase hanging off (where it meets up to the back of the tranny). So I got a squeeze clamp and put it back on. Not sure what that goes to but probably something for the tranny since it wasn't on the tcase itself. So I still have to try unplugging the brown wire. Does that just unplug from the tcase casing or does it unplug somewhere else? And the speed sensors are boltted to the tcase it appears. I'm deffinately going to try the drive shaft test you suggested. Do you recomend pipe wrench for that (my channel locks suck)?

Also I'm going to try to stay off the 911 threads unless it becomes an emergancy by there discription. So, on this particular issue I'm going to keep my posts on this thread. I feel like I should be paying you guys for this valuable info. I do really appreiciate it guys. oh yeah I checked out the pics gijoe. Nice trucks!

 

[tcross8361]

OK, simple check.... Jack the front end up with the key off and try and turn the front driveshaft. You may need a good pair of channel-locks to get it to turn initially, especially if the front brake or wheel bearing is giving you fits (more on that in a minute). If the front driveshaft will turn one full revolution, the transfer case is NOT locked-up. Also, if the transfer case was locked in 4 high, there would be other tell-tale signs.... binding noises and/or hopping when turning in a tight circle as the driveline binds-up.

If the brake or wheel bearing on one side is dragging excessively, when you jack the front end in the air, the front driveshaft will try to drive the "free" wheel twice as fast as normal. (like when you spin one rear wheel of an open diff). In general, if the front driveshaft will go more than a single revolution, it's free enough that it's fine.

The root of your problem could still be a brake caliper frozen-up or a bad wheel bearing causing the heat.... or have you ruled them out in another way?

-Joe

ok, I got it to turn and it kept turning so i guess the tcase is good right. It did turn kind of hard but it did turn. Probably need to do my front brakes and my ball joints then. I guess it should be good to go then. Like I said before I've never delt with these types of 4wd's before. I've always had manual 4wd's. I kind of miss them. I guess you learn something new every day. Thanks everyone. I'll still be browsing the threads from time to time. Very interesting stuff.

 

[gijoecam]

Not a problem.... glad you got it figured out....

New technology, new stuff to learn.

It actually is a pretty durable and reliable system for the average user. Hard-core wheelers and those that really abuse the drivetrain tend to see more failures, but that's nothing abnormal.

It's also good to know all you can about your rig, in the event it attempts to leave you stranded. Armed with the knowledge of what's supposed to work how and why, you've got a better chance of bailing yourself out when the going gets tough. Example right here.... you now know how your 4wd system is supposed to function, and what to check to make sure nothing's wrong. The next logical step is to figure out how to MAKE it work when it won't.... that would entail forcing the 4wd..... a jumper wire here and there and you can force the 4wd to engage if for some reason the GEM takes a dive, switch comes un-plugged, etc. Simply apply 12 volts to the clutch connector and boom, you're back in business.

Glad we could help out!

-Joe