97 Transfer case not shifting

[SpyrDragon]

So when i bought my 97 5 speed, the guy told me that the transfer case worked. Well, I went and checked and it does not appear to be working. He already had the shift motor replaced as I could tell when I was under the truck trying to fix the speedometer. Here's what's happening:

I start the truck and both the 4WD and 4WD Low lights come on during the bulb check then go off as they should. I turn the switch to 4HI and the 4WD light comes on, but i dont hear any clicking or anything indicating that it shifts, not even hearing the trasfer case shifting. When I put it in Neutral with the clutch down and the brake pressed, I switch it to 4LOW but nothing happens at all, the 4WD Low light doesnt even come on.​

The other thing i noticed is that every single time I turn the truck on, even if I don't start it, I can hear the Transfer Case relay (the little gray box behind the radio next to the GEM) clicking several times. I'm not sure if the relay could be causing the problem; want to see what else I can find out before spending the money to replace it. As far as diagnosis, here is what i managed to find out:

I had a scan tool hooked up looking at the 4X4 datastream coming from the GEM. I can confirm that the switch is good as the GEM is getting output from the switch. I could see the switch postion reporting correctly. When I switched to 4HI, the GEM reported that the transfer case was switching to 4HI, but the readouts showing the transfer case clutch positions did not change as if the transfer case wasn't attempting to shift. When I tried 4LOW, the tranfer case clutch postions still didn't change, but the GEM was reporting that it was still in 4HI and did not switch to 4LOW even though the switch requested it. I also confirmed that the front and rear speed sensors are working; put it in gear and got a speed readout on both.​

I do plan on looking at the wiring diagrams for the shift module and make sure that's all working right. I was hoping to see if anyone else had a similar issue. I was mostly curious about the shift relay clicking everytime the key is turned on and if it might be related at all. I searched everywhere but couldn't find anything. Hoping someone may be able to help me out here. Oh and yes, I did check all of my fuses and every one of them is good so that's definatly not an issue.

Thanks.

 

[410Fortune]

good job on the prognosis thus far
In my experience unless there is a broken wire the t case shift motor is almost always the cause of this.
The 4hi light should NOT BE ON in the dash unless the motor has actually turned to that position, I do not think its possible to get a 4hi light without the motor turning to that position? I could be wrong.

Try tapping/rapping on the side of the shift motor while trying to get the 4hi to shift? any changes?
Remove the t case shift motor from the t case, will it turn now (still wired up)
Can you manually turn the t case from 2wd to 4hi?

Next step would be to inspect all the wiring, pins and clips down at the t case
Then I would un pin the brown wire and take the t case shift motor to the bench, take it apart and see whats up inside.

 

[SpyrDragon]

I’ll try some of this out whenever I have a better chance to look at it. I didn’t really think that the motor could be bad seeing as how it already has a new motor already, but I guess it could be bad. I’m still wondering if the shift relay is bad cause it clicks several times with the key on.

 

[drdoom]

If you have ForScan you can do a GEM self test. It is done with the truck running, and prompts you when to shift to neutral, hold the brake, etc. Not sure if that helps, but I did want to inform you.

 

[Mbrooks420]

Your 4wd high might be functioning correctly. There is no shifting between 2wd(or 4wheel auto) to high.

 

[410Fortune]

AHHHHHHHHHHH yes the control trac
mrbrooks = smart man

 

[SpyrDragon]

Update:

So I went ahead and replaced the transfer case relay just to take a chance on it and it did not fix it. Im going to look over the wiring diagrams and hopefully get under there and start testing everything at some point this week. I'll report back with any findings.

 

[Gimpy117]

I have a broken 1995 that I would rob the t case motor off of. would that work?

 

[410Fortune]

Should work yes.
The wiring plugs at the motor itself may have changed
95 is also control trac?

 

[drdoom]

So has the speedometer been working?

 

[SpyrDragon]

Forgot to post an update the other day. So i found out that when the last guy replaced the motor, he had just twisted the wires together and i thought that was causing the problem, so i ended up reconnecting them with butt connectors, but that didnt fix it. I ran some other tests and lo and behold, the shift motor is actually bad somehow.

I was able to force the motor to shift by grounding out the wires on the shift relay and i had a scan tool hooked up and could see the clutch plates moving. I followed a pinpoint test by jumping the pins that report the clutch plate postions and it turns out that the plates arnt engaging as they should and arnt reporting their positions correctly so the GEM is refusing to let it shift. Looks like I'll be replacing the motor afterall, altough i probably wont be able to until some time in the next few months or so. I may end up pulling it apart first and see if there is anything i can do with it before replacing it.

 

[drdoom]

Fine, but what about the VSS? Did you get it working? Reason I ask is on some systems you cannot get a shift to 4LOW without a zero reading at the VSS, even in neutral with foot on the brake.

 

[410Fortune]

dang t case shift motors have been causing people this grief since they first came out

Take that SOB apart and let us know what you find

 

[drdoom]

dang t case shift motors have been causing people this grief since they first came out

Take that SOB apart and let us know what you find

Majority of that grief is self inflicted because so many people think the shift encoder motor is what engages the front wheels!
Edit: I am on that list! I have had on the shelf for fifteen years a perfectly good encoder that I changed out unnecessarily. What actually the transfer case needed was bushings, fork enhancement, and a rebuild.