4wd Problems

gmtech4 · April 29, 2013

im in alberta now lol,,,,,,i hate the oilers and calgary !!!!!

VMaxtastic · April 29, 2013

One thing ive noticed with all three of my gmc's over the years 2000,2007,2013, is that unless i back up after disengaging it, i will hear the transfer case whining away like its still in 4wd.. Even when i set it to auto.

Has anyone else noticed this?

gmtech4 · April 30, 2013

did you take it in for warranty ?

VMaxtastic · April 30, 2013

Have on my 07.. Was told its normal. Mentioned it with my '13, as well as vibration under heavy acceleration, in 2wd. Waiting to find out about it when i get home from Mexico. Was wondering if anyone else experienced the 4x4 thing

90softail · December 22, 2016

Just some added information on this problem, I have encountered several trucks with this problem, following proper diagnosis is always the correct way to go and it has led me to the solution, tan wire going to encoder motor will be corroded and severed by front cab mount on left side, near ground connection, open harness carefully, and the green cheese of corrosion is quickly identified, usualy within 12 inches of mount, repair all wires affected, clear codes and retry, this circuit goes to actuator motor lock circuit controlled by pcm, it sends a ground signal, unlocking actuator, with this circuit incomplete, shift encoder motor will not unlock, and shifting is prohibited, I hope this helps others encountering this problem, I have repaired several, with identical problem, but remember following diagnostic, code related procedures is how I found this! Merry Christmas, and Happy New Year! !!!

GhostWriter · December 24, 2016

Remarkable how durable some these components are, as long as the wiring remains intact.

Wardsilverado · December 29, 2016

I have an 07 silverado(new body style) 1500 Z71 4x4 and have been having problems with locking my truck in for quite a while. I read solution after solution on truck forums which there are many. I have the dial on the right side of steering wheel. It's 2 high, auto, 4 high, 4 low. I was getting service 4wd light and the light on the 4wd switch would blink for like 45 seconds when switching from 2 high to auto. It would say it was locked in but nothing. It was locking in at the transfer case but not locking in at the front differential. Had it on a hoist and put it in auto and then put truck in gear-front driveshaft turned but front tires didn't turn. I put in a new actuator and that worked fine for 2 weeks when the same problem occurred. Tired of trouble shooting and not having the 4x4 working so I came up with an inexpensive repair. I removed the actuator from the front differential and used black electric tape to tape a washer and a nut onto the end of the actuator. This is enough to engage the front differential and get the front wheels pulling when in 4x4. When unlocked the front diff is still engaged but not pulling as the transfer case is unlocked. I plow with my truck and this solution has worked great and solved a ton of frustration and money

Brettman · May 14, 2017

On my 2006 that was what the manual had stated to do and it had the auto 4 as well. I had to do that once to get out of 4wd and it worked.

Thanks, I'll try that on mine today

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Brettman · May 14, 2017

Guys - at the end of the day my truck was fixed. I started a new thread here that basically continues and finishes the discussion:

http://www.gm-trucks.com/forums/index.php?...&hl=encoder

The end result was that I replaced the encoder motor myself and it didn't fix the problem. Took it to the dealer as they are the only ones that I know of that have a scanner that can read transmission fault codes (my "service 4WD" light was on). It ended up that my transfer case control module (TCCM) was bad and needed to be replaced. That cost me $886 out the door on top of the $180 or so that I already spent on the encoder motor.

To the original poster: the dashboard switch is the most common problem. The next most common problem is the encoder motor. The fact that yours still functions makes me think that you could replace the sensor and be good to go. If you search hard enough you will be able to find a part number for the sensor and buy it off of gmpartsdirect.com. If that doesn't fix it you might be looking at a TCCM. You can go to a junkyard and find one cheap; or do like me and take it up the rear. Since my truck was stuck in 4WD I had to get it fixed fast. I didn't have time to search for the part at a junkyard.

From what I have learned over recent weeks about the 4WD system it sounds like you are having an electrical issue since the 4WD still works. If you want to keep your truck from putting itself in 4WD as a temporary fix you could just remove the encoder motor and manually put it in 2WD. Or, if you know the truck is already in 2WD just un-hook the encoder motor and it will stop shifting it. This is a temporary fix but one that might save you headaches until you can find the time to really diagnose the problem!

Good idea I will do this myself on mine, thanks guys

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