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Transfer Case Engagement Issues

Glacier991

EF Tranny Guru
Moderator Emeritus
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City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Originally posted by Sparky1973:

"this is a different topic and hopeing glacier can help in some way. i posted this on the new member form and didnt get any help. glacier you sound like you know what your talking about. heres my probly i have a 97 exsploder. truoble with front wheel drive. ive checked all the fuses that have anything to do with the 4x4.nothing there with know weight on the wheels the front pulls good but when i put the front end on the ground ithardlypullsall. it does this in all modes. dont know if it could be a fluid problem. or maybe a voltage problem, or are the clutches just gone in the transfer. hope not. also was wandering if someone may have done the brown wire thing in the past i havnt found a switch though. any help would be great.

thanks

Jeff"
 



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Folks, let me do a little disclaimer here. I am no Transfer Case guru. at all. I do intend to educate myself on them and even do some Diaries on rebuilding them so we can all learn together. There are others with much better knowledge on them than I, and I am asking THEM to chime in here.
 






glacier thanks for replying. i was hoping for more info but hey i understand I wish i knew everything too. if anyone can help me on this or give me some idea. or has had the same problem please let me know. again thank you glacier. Jeff
 






Mine is still working ok, but I have seen some people with a transfer case clutch that isn't working and gives the symptoms that you describe. In one case, the wrong lube may have been used (gear oil ipo Mercon ATF). In the other cases, they were hard core offroaders with larger than stock tires.

I would check for current on the brown wire to rule out an electronic problem. A good access point is the connector right next to the transfer case.

Here is a couple of links with similar issues:

http://www.explorerforum.com/forums/showthread.php?t=61181&highlight=transfer+case

http://www.explorerforum.com/forums/showthread.php?t=61078&highlight=transfer+case
 






hehe my body hurts (no sleep) ... anyways, yeah the first thing id check is the fluid level on the transfer case.

as you and others have mentioned, your friction plates could be worn out. i have taken apart a BW4405 transfer case from the same year as yours (1997) and the friction material just fell apart as soon as i lifted the friction rings from the transfer case.

also, your suggestion of the "voltage problem" is possible and if this is the case, then the electromagnetic ring is not being powered up enough to squeeze the friction rings together. i guess you could take a multimeter to the "brown" wire and see whats running across that wire and maybe ask your local ford dealer for reference values to check against.

the other possibility is that the "balls and ramp gear" system is just not working. my old 1998 BW4005 had a cracked gear and when the gear cracked, it didnt just crack in half. instead, it cracked in two large parts and a few smaller pieces. if the missing pieces leaves gap(s) large enough to allow one (or two) of the metal balls to sit inside, then there might not be enough pressure on the friction plates to engage the front driveshaft. see my thread on this cracked gear problem.

though it is possible, i am doubtful that the problem lies in the electromagnetic ring not being powered up. i am leaning towards the friction plates/rings issue though the cracked gear, as I believe Glacier pointed out in one thread, does happen a notable amount of time.

below is what the rings looks like, your's obviously is the one labelled "97" on the left side so ignore the one on the right. i cant remember exactly how many "rings" there are per set but i think somwhere around ten.
friction_plate.jpg

dunno if this is useful but just in case you decide to open the transfer case, this is what the electromagnetic ring looks like:
plugs_elecring.jpg
 












Glacier991 said:
Folks, let me do a little disclaimer here. I am no Transfer Case guru. at all. I do intend to educate myself on them and even do some Diaries on rebuilding them so we can all learn together. There are others with much better knowledge on them than I, and I am asking THEM to chime in here.


I'll give you a call when mine bites the dust. ;)

Looking at the pictures from the other thread and knowing a little bit about how the 4405 operates - I would describe it as sort of a hybrid between a standard t-case and an auto trans. It has a chain driven front shaft which is engaged by a clutch pack very similar to an auto transmission. The main difference is that it uses a "ball ramp" mechanism to engage the clutch plates instead of hydraulic pressure like an auto transmission. The ball ramp mechanism is activated by an electromagnetic coil which gets current from the TOD solid state relay. The relay is turned off and on by a PWM signal from the GEM.

I have never had to work on mine (other than fixing a leak at one of the speed sensors) but I think that it is a really interesting design.
 






ok guys heres the deal now. i drained the fluid it looked ok now metallics. put new fluid in and even added a little lucas trans additive. still the same deal. so i took the servo motor off again. put 12volts to the yellow and orange wires that go to the motor and the motor works foward and reverse. but i have no power at the selector switch on the dash. i checked it without anything hooked up at the servo motor not sure ware that switch gets it power maybe i have to plug in the servo motor. if ware might i find the problem. i have checked every fuse with a test light they are all good. ware should i go next guys ? also on the brown wire conversion deal is this the big brown wire that goes in the trans case. could i have a bad sensor in the t-case. please help help help. anyone know ware i can find a wiring diagram on the 4 wheel drive.
thanks guys.
Jeff
 






sparky1973 said:
i have no power at the selector switch on the dash. i checked it without anything hooked up at the servo motor not sure ware that switch gets it power

The switch is actually just 3 resistors that the GEM "reads" to determine the switch setting. So you won't get power at the switch. Check this to test the switch:

http://www.explorerforum.com/forums/showthread.php?t=145334&highlight=transfer+case+switch


is this the big brown wire that goes in the trans case. could i have a bad sensor in the t-case.

Affermative (yes). The big brown wire leads to the coil inside the t-case that actuates the clutch. You need to see if you have current in that wire.

P.S. I can post a schematic later this evening. Edit: See next post, I forgot that I already posted these in my gallery.
 












well dogfreind im still lost just put it back together the way it was. before i started trowing tools. i actually took the servo motor off and put the t-case in 4 high and still very little front end pull. im gonna buy a new switch and hopfully thats the problem. ware can i get a switch at is it a ford dealer part or can i get one at advance auto parts. it the switch dont do it im gonna try the sensors on the t-case. i know the motor is good because it works when i put power the the yellow and orange wires. but with the motor off the t-case but still hooked up the motor does not move when switch is moved. even with the motor grounded. also what are these guys getting the manual cases out of and how much are they running dollar wise? im starting to lean towards going that route. thanks for all you info.
 






I will break out my BW 4405 thats not being used and check this out because I'm starting to think this is a mechanical problem. I have classes and such all day tomorrow so I'll reply back on Thursday.
 






sparky1973 said:
well dogfreind im still lost just put it back together the way it was. before i started trowing tools. i actually took the servo motor off and put the t-case in 4 high and still very little front end pull. im gonna buy a new switch and hopfully thats the problem. ware can i get a switch at is it a ford dealer part or can i get one at advance auto parts. it the switch dont do it im gonna try the sensors on the t-case. i know the motor is good because it works when i put power the the yellow and orange wires. but with the motor off the t-case but still hooked up the motor does not move when switch is moved. even with the motor grounded. also what are these guys getting the manual cases out of and how much are they running dollar wise? im starting to lean towards going that route. thanks for all you info.


I lost a 10mm wrench once because I tossed it and never found it again. ;)

I think your shift motor is working fine; the problem is that the internal clutch that sends torque to the front driveshaft is not working correctly. It is possible that it is an electrical problem where there is no current (on the big brown wire) going to the coil inside the t-case. The other possibility is that the clutch is worn out or otherwise damaged.
 






This should be a very simple thing to narrow down. Using a multimeter, engine on, switch set to 4x4high, check for 12V at the brown wire near where it goes into the transfer case. If you HAVE 12V but no four wheel drive (i.e. you can still turn the front driveshaft), you need to tear apart the transfer case. If you DON't have 12V, you should, and the problem is likely either in the GEM or the wiring going to the xfer case.

Another thing is to not forget that there are TWO components that actuate the transfer case clutch coil: One is the TOD relay (in auto mode) but the other is the transfer case shift relay (in 4x4 high and low). I also know that if you interrupt the feed from the TCS relay, the TOD relay is still active even in 4hi and 4low, so it will still try to get you around in 4wd.

With that in mind, even if the TCS relay was on the fritz, you should still have 4wd.

Another thought: With the truck in the air on stands, there may be enough resistance in the transfer case clutch discs to keep the front end turning even if the 4wd is not engaged.

Also, I like the analogy about the automatic transmission, but I consider it to be a cross between an automatic transmission and an air conditioning compressor. OR, if any of you have ever worked in a stamping plant, a wet-clutch press works almost the same way (without the dynamatic brake to stop it, of course).

-Joe
 






Transfer Case + Auto Trans Clutch Pack + A/C Compressor Clutch + Computer = Control Trac ;) :D
 






wow i wasnt exspecting all this help soo quick you guys are great. thanks i will check the power to the brown wire tomarrow night. so if i dont have 12v to it i should be able to put a toggle inline with a power wire and controll it that way shouldnt i? this is my wifes ride. so all i need is 4 high in the snow. my ride is a 01 f-150 3" lift 33's prerunner. working on roof mounted light bar and thropy truck style roll bar with spare mounted on it and a turbo gate. thaks for all your help guys . jeff
 






sparky1973 said:
..so if i dont have 12v to it i should be able to put a toggle inline with a power wire and controll it that way shouldnt i?..
yes that would work though i would be careful because a straight run to an electromagnetic ring is basically a short circuit.

hmm thats interesting, i wonder if the current going to the ring is "pulsed". hehe if you've got an oscilloscope, hook it up and look for a wave ;)
 






hey dogfriend, sorry i edited your message!!! VERY SORRY :mad: !!! anyways, here's what you said:
dogfriend said:
Yes, according to the original patent, and other info that I have in the shop manual, the current going to the coil is pulsed on and off in 4wd Auto. The GEM supplies a PWM (pulse width modulated) signal to the TOD solid state relay. The signal is varied by the GEM to try to keep the front and rear driveshafts at the same speed. When traction is good, in 4wd Auto, the pulses are very short - when the GEM determines that the rear wheels are slipping (when the rear driveshaft is turning faster than the front) it increases the length of the pulses to send more torque to the front wheels.

Another interesting point is that (as gijoecam mentions) in 4wd Low, the current is sent directly from the TCS (transfer case shift) relay, so the current is on all the time in 4wd Low.

Thats interesting that its on all the time when in 4LO. :D
 






I will post some of the manual description:
 

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