Hi all it has been awhile sence I've been on here. My dad is haveing problems with his transfer case. He has a 2001 F-150 4x4 with the 7700 package(7lug axles). He has had the transfer case rebuilt 3 times. It seems to be having the same issues. He just had the shaft replaced in June. While driving it home from the shop it deffinatly was in low range. My dad said it made a loud clunk and then another. To me it sounds like it went to shift into low on its own. This could be why the t-case keeps breaking. Has anybody else have had or herd of this problem. I don't want him to keep rebuilding the thing and have it continue to break. I'm thinking it maybe something wrong with the gem. Could be sending a signal to shift when it should't. If anyone has any info please let me know.

Thanks allot Bob

 

Since this is what is going on and getting expensive, it's time to learn how the system works and understand a few points.
....As an overview; for 4H, the dash switch in that position 'request' the Gem to operate the transfer case motor to it's (first) position rotateing a shaft in the transfer case to change power flow through the transmission to the front output shaft, and operate the vacuum actuator on the front axle to engage the front wheels.
....In 4L, you must stop the truck, put selector in neutral and apply the foot brake, then select 4L.
....This requests the transfer case motor to rotate to it's (second) position changing the power flow again through the transmission to a lower overall gear ratio.
....A the same time, a signal; is sent to the PCM changing shift skedules because of the large change in overall gear ratio that occurs.
....The stopping of the truck and the engagement procedure for 4L is to prevent a driver from doing this 'on the fly'.
A huge change in overall gear ratio could send you and passengers hard against the dash and cause an accident as well as break something in the transmission.
.
What you now need to do is see exactly what happens and when so you can get some idea of what the cause might be.
Is the 4x4 going to 4H by it'self?
Is it really going to 4L with attendent low overall gear ratio?
What does the dash lamps tell you each time.
Does the windshield leak on the driver's side?
Unless you look at it from a position of knowledge, no one will have a starting point for what's going on.
I wish you luck in solving the issue.

 

I know how the system works. It is trying to shift into low when at highway speeds. This would be why it has snapped the gear shaft in the t-case 3 times. He has had the thing at 2 diffrent shops. I use to be a mechanic I just haven't had time to fix it. A good mechanic would realise that something else is wrong for the same thing to happen over and over. The last shopped is were I helped him drive it back from. They of corse wanted to charge him 1800 dollars to chage out the transmission which works fine. Nort wanting to fix the t-case under warenty. You can put in all the fail safes you want but when you have a falty control module or a short funny things will happen. Now that I'm done explaining it better so I no longer get smart-alleck remaks.

First I checked for leaks in the window. It does not appear to be leacking at all. I was asking the question to see if anybody else has had this problem. To help me out, or try to rule out things befor I get into it anyfuther. I belive either the gem or the harness may have a short sending a false signal to the shift mottor when it should not. I know fords wire and gem moduels are of great quality.

Thanks for anybodys help Bob.

 

BOB, i'm sorry to have offended you.
I had no way to know what your experience level is or what else has happened in this situation, until your reply had indicated such.
Sorry you took it that way.
I will not try to help any further now that I know your hostle towrd me.
Good luck.

 

Unhook the actuator motor on the t-case and run a wire to the 4wheel low side in the harness with a light in the cab to see if it is doing this at a sertin speed or random.
I would unhook it to prevent any more damage tell you could get the time
Sometimes shops like repetitive business just for the cash And they think the owner knows nothing I know this is not the case here but some times to get the job done right you need to do it yourself
Remember the people here are just here to help
Also any mice been in the truck eating wires
This happened to me 99 f150 up by the switch and crossed the power in to the high side so it would engage in high hitting bumps and potholes
Good luck

 

Sorry bluegrass. I didn't explain it ehough. I have't been on here a while and thought you might of been one of those that answer with sarcasum instead of helping. There was nothing ment by it. To the other fellow that answered thanks allot. That is something I was leaning twards. I need to get ahold of a scamatic to find out which wire does what. I was thinking of takeing the shift motor off and trying to shift it by hand back into 2 hi so dad can drive it. Until I get it figured out.

Thanks allot guys Bob.

 

Your local ford dealer can print off the diagram for you usually free well they have never charged me
It may depend how good of a relationship you have with them
Good luck

 

Take the motor off, shift the drive shaft back to 2wd then leave the connector off so it can't move again until you get to looking at the electrical circuit.
It may be an intermittant cross with 12 volts at some point causing the motor to move in one direction.
Note that to reverse the motor direction, the 12 volt supply is reversed in the circuit when returning to either 4H or 2WD from 4L.
It's always possible the GEM might do this but never heard of this yet.
Usually if the GEM is subject to a windshield leak the water causes corrosion that become conductive, then funny things begin to happen at different times.
Might be an idea to monitor the feed line at the motor's forward direction lead and move the harness around at different points to see if the test light flashes indicating the cross or cause, or leave the motor connected and hanging loose.
Also look closely at the motor circuit board strip and contacts for an issue. This board's contacts sends back position data to the GEM.
Good luck.

 

Thanks allot guys for all te help. Hopefully I will have time to look at it this Saturday. Me and dad work different shifts

Thanks again Bob.