I can usually find all the information I need without having to post, but not this time. I have a 2001 super crew 4x4 with the electronic shift system. When I put it in 4x4 my front driveshaft locks up as it should, and I can see the front cv axles try to turn as I wiggle the drive shaft, so I know the vacuum system is working as well, but my transfer case isn’t engaging. Does anyone know what wires on the motor I should test to see if the motor is bad before I go buy a new one? Another weird part to this problem is that when I try to put it back in 2wd the 4x4 light stays on, and the gem is still grounding the 4x4 solenoid, rather than the 2wd solenoid on the firewall. If I disconnect the battery for a second it fixes the issue, until I put it back in 4x4, then it does the same thing. I’m not sure if the transfer case motor being bad could cause this or if the gem is bad and causing both of these issues. Any help would be greatly appreciated as I’d like to get this figured out before winter sets in.

 

Watch this video. It will guide you in the correct direction. Testing solenoids and gem first, pull the vacuum hoses off actuator make sure you have vacuum to the correct lines. If you have vacuum to both lines it's a bad 4wd switch. At least it was for me.. Rock auto is the cheapest for the switch.


The transfer case motor will give you a code. So if no code, not the motor.

From the problem your explaining I'd think it's the switch.

 

I’ll give that a try when I get off work today. I checked the resistances on the switch earlier and they were correct. I think the vacuum system is working because the driveshaft locks up when I put it in 4x4 and as I turn the driveshaft a little each way I can see the cv shafts wiggling as well, which should mean the front axle is locked in. The part that’s confusing me is that when I take it down a gravel road it’s obvious I’m not actually getting power to the front wheels. Which is why I was suspecting the transfer case motor. The thought crossed through my mind that maybe the vacuum reservoir is cracked and it’s not holding like it’s supposed to under power, but surely if it was going in and out down the road I’d hear some clunking and what not, which I don’t.

 

If you prove it all the way through to the vacuum actuator working, the. It is probably the shift fork inside. Seems to be quite common. Watch this to see what I am meaning.

hope that helps!

 

The front end is working properly as I suspected. I pulled the transfer case motor the other day and it is in fact not engaging. It looked like it was the original one and it wasn’t too expensive so I figured I’d go ahead and replace it. Got the new one in and no change. Anyone have any ideas on what could be not functioning properly?

 

Your post indicates you show 4x4.

If this true , your shift motor is working

There is electronic position feedback in the shift motor...it doesnt show this unless
Its in that position. This is why the delay when turn switch, the motors turning a worm gear. When it loses this position..mismatch..the whole system goes dead. No lights.

So, either your gem/wiring is bad somehow, or something youve said is wrong. It does a self test on startup, and disables system if doesnt pass.

 

To clarify for OP, So what your saying is, if 4 x 4 doesn't show when turning it to 4 x 4, and the front axle is fully operational, its the gem wiring or the transfer case motor?

So when 4 x 4 doesn't show, it could be transfer case motor without coding?

If it does show 4 x 4 after engagement and front is working fully, gem wiring?

Something isnt adding up huh?

Mine works sometimes and doesn't others, so that worm gear I'm sure is plastic and the cause of it not working. Sorry I'm typing as I think..lol

 

I personally think I have a gem problem, I’m trying to see if anyone has a good way to test this before I go buy one. But yes, when I turn the switch to 4x4, the dash light comes on like normal, the front end engages as it should, but the transfer case motor does not move. Then to add to the issue when I turn the switch back to 2 high, the 4x4 light stays on, and the front end does not disengage. Disconnecting the battery, and reconnecting it turns the 4x4 light off and unlocks the front end.

 

Also thinking as I type lol. I guess the better question to ask would be, is there anything left to test between the gem and the transfer case motor? Or is this obviously a gem problem at this point?

 

I'd check your 4 x 4 switch again. Thats still my bet.

Try this - once in 4 x 4, go underneathe check to see if you have vacuum on the front axle. Obviously you have vacuum but I'm betting you have vacuum to both lines at once on actuator. You should only have vacuum to one. If you have both lines with vacuum the switch is not relating on /off to the correct solenoid.

I've had this happen and replacing the switch fixed it .