4wd Problems

seadoons · March 26, 2009

Even with the auto 4WD system...with the system in 4wd - it will disengage by driving backyards? That would be great if it would.

jaycutler24 · March 26, 2009

Even with the auto 4WD system...with the system in 4wd - it will disengage by driving backyards? That would be great if it would.

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.

seadoons · March 26, 2009

Went by the dealership tonight - they tell me the encoder motor needs to be replaced. $685 for the part; $285 for labor - so over $1000 out the door. I have searched this site for the part number and I can't find it - is this an easy job to do myself? The truck is stuck in 4WD Hi right now - will that impact installing a new motor??

hockeypro1411 · March 26, 2009

Went by the dealership tonight - they tell me the encoder motor needs to be replaced. $685 for the part; $285 for labor - so over $1000 out the door. I have searched this site for the part number and I can't find it - is this an easy job to do myself? The truck is stuck in 4WD Hi right now - will that impact installing a new motor??

Shouldn't matter.

seadoons · March 26, 2009

So I could, with the truck in 4WD, unbolt the current encoder motor and install a new one, start up the truck and shift it back into 2WD with no problem? I have found the part on ebay for $200. Found it on gm parts direct for just over $400.

Terry2001 · April 6, 2009

Hello,

Have a similar problem.......

1. Stuck in 4HI,

2. "Service 4WD" on shortly after every startup, stays on.

3. NO lights on dash switch indicating 2HI, 4Lo, etc...(except all flash momentarily on startup, typ.)

4. Pushing switch buttons does not appear to effect anything (no sounds of trying to engage/dis-engage)

5. no real action to cause problem, just driving paved side street 4WD came on, switch lights went out and then noticed in 4WD by feel of the drive.

Checked fuses in the dash panel and under the hood, all were good.

Checked for loose wiring, appeared/felt fine.

Swapped out the switch for a known working, no change.

Tried my switch in a known working truck and it was fine, all worked.

To disengage the 4x4 I disconnected the negative terminal of the battery, reconnected after a few minutes and I was in 2wd. Moved the truck back and forth and it stayed in 2wd, as soon as I pulled out onto the road and drove maybe 50 yards it went back into 4wd. Tried this procedure twice and each time it would disengage for only a short drive. Based on this I am guessing that the encoder motor is fine but may instead be the encoder motor SENSOR? (thought this may help you get your truck into 2wd to replace the encoder motor).

Any tips for me based on your problem/solution would be appreciated????

2001 GMC Sierra 1500

Thanks,

Terry

BretD04GMC · April 6, 2009

I had a 4WD issue with my truck not long after I bought it back in 2005. The first time it was the software. A few months later it popped up again. The second time it was the 4WD sensor. The dealership fixed everything under warranty.

In my case, the indicator lights on the 4WD switch went out and I got the "Service 4WD System" message on the DIC. I never had the truck get stuck in 4WD.

Z71kris · April 6, 2009

Nathan,

What is the status of your truck?

seadoons · April 6, 2009

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!

Terry2001 · April 6, 2009

Thanks for the info. I have since (in the last hour or so) figured out a way to keep it out of 4wd (without going under the truck), thought I would share for others that have a similar problem:

1. Remove the negative cable from the battery, wait a few minutes (3 minutes worked for me).

2. Reconnect the negative (ground) cable to the battery.

3. Start the truck only (do not put it in gear, do not hit any buttons etc...)

4. While the truck is running remove the "ATC" fuse from the fuse panel in the engine compartment.

(not a pro so this may or may not be an advisable technique!!!)

5. Test drive to ensure 2wd.

This has worked for me......so far.

I am now trying to source a TCCM to test as that is the next "easiest" item to test. If that does not make a difference I will then move on to the encoder motor (and/or sensor). Hoping to find a healthy volunteer to temporarily swap parts.

Thanks,

Terry

seadoons · April 7, 2009

Terry - I think that fuse controls the encoder motor. So, if you pull it then the encoder motor won't be able to change gears - and if the truck is in 2WD when you pull it you are all set.

FYI - the encoder motor was surprisingly easy to change. Good luck with all of this.

rwregener · April 7, 2009

Nathan:

Was pulling the front drive shaft easy?

I've got service manual instructions that show a clamp style boot at the transfer case end of the drive shaft. It says that you need to install new clamps when you reinstall the drive shaft.

Did you have to replace with any clamps?

seadoons · April 7, 2009

Ah yes - removing the driveshaft. That was the one thing that almost kept me from trying this repair as I am a total novice when it comes to car repair. Honestly - removing the driveshaft was teh easiest part of the job. I did see in my manual where it says to remove those clamps - DONT do that. This is what I did:

1. Set the parking brake.

2. Use a permant marker to mark the position of the drive shaft.

3. Look at the front of the driveshaft where it attaches to the front differential. There are four bolts that hold that joint together. Take those off. Each set of two bolts holds a metal piece on - those two metal pieces will come off with the bolts (there is one on each side of the driveshaft).

4. Push the driveshaft back towards the transfer case - this will allow you to drop the front end out of the joint. Then, give it a good tug to slide it out of the transfer case. When I say give it a good tug - I say that because that rubber boot that you mentioned above has to get over a little lip - it will be easy though.

The driveshaft is relatively light in weight. You really have to move it in order to get to one of the bolts on that encoder motor. Re-installing the driveshaft is the exact reverse of the instructions above. Just line up your marks and you'll be good to go.

One more tip - that part of the driveshaft that you will slide out of the transfer case has a bunch of small grooves on it. When putting the driveshaft back in it is easy to put it back in off by one or two of those grooves. The way you will be able to tell this is that the front part of the driveshaft won't seat back correctly and you won't be able to get the bolts and clamps on properly. This is no big deal - just slide the shaft back out of the transfer case and make your adjustments as necessary. I had to do this twice. Also - be sure to torque those four bolts back correctly. Don't quote me on this - but I think they are 15 LBS (check your manual).

***Disclaimer - I am not a mechanic!!***

philzinn · December 5, 2009

Nathan:

Was pulling the front drive shaft easy?

I've got service manual instructions that show a clamp style boot at the transfer case end of the drive shaft. It says that you need to install new clamps when you reinstall the drive shaft.

Did you have to replace with any clamps?

I used a zip tie and it seems to be working fine.

philzinn · December 5, 2009

Ah yes - removing the driveshaft. That was the one thing that almost kept me from trying this repair as I am a total novice when it comes to car repair. Honestly - removing the driveshaft was teh easiest part of the job. I did see in my manual where it says to remove those clamps - DONT do that. This is what I did:

1. Set the parking brake.

2. Use a permant marker to mark the position of the drive shaft.

3. Look at the front of the driveshaft where it attaches to the front differential. There are four bolts that hold that joint together. Take those off. Each set of two bolts holds a metal piece on - those two metal pieces will come off with the bolts (there is one on each side of the driveshaft).

4. Push the driveshaft back towards the transfer case - this will allow you to drop the front end out of the joint. Then, give it a good tug to slide it out of the transfer case. When I say give it a good tug - I say that because that rubber boot that you mentioned above has to get over a little lip - it will be easy though.

The driveshaft is relatively light in weight. You really have to move it in order to get to one of the bolts on that encoder motor. Re-installing the driveshaft is the exact reverse of the instructions above. Just line up your marks and you'll be good to go.

One more tip - that part of the driveshaft that you will slide out of the transfer case has a bunch of small grooves on it. When putting the driveshaft back in it is easy to put it back in off by one or two of those grooves. The way you will be able to tell this is that the front part of the driveshaft won't seat back correctly and you won't be able to get the bolts and clamps on properly. This is no big deal - just slide the shaft back out of the transfer case and make your adjustments as necessary. I had to do this twice. Also - be sure to torque those four bolts back correctly. Don't quote me on this - but I think they are 15 LBS (check your manual).

***Disclaimer - I am not a mechanic!!***

Sometimes there is a large groove in the spline so that you can only put the shaft back in in one position. On this transfer case it is easy to not get them lined up. I did not get mine lined up, and I think that I am off, but I don't know how much. Now I have a slight vibration from the drive shaft. But I don't know if it is from the transfer case side, or if I got the front U joint slightly out of line in the front yoke. Any ideas?