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2003 Silverado Transmission/transfer Case Issues


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I've been having increasing problems for a few weeks with the 4WD. I would be driving along in Auto 4WD and I would receive the message "Check 4WD..." on the DIC. The transfer case would make growling sounds when this happens. I would stop the truck, cycle the ignition, and the problem would go away. It's done this for several years, but it would rarely happen. Now it's happening many times a day, but cycling the ignition still fixes the issue. I'm aware of the switch and encoder problems and will look into that.

 

Coincidentally or not, I also had a transmission issue on Sunday, about an hour after the Michigan snow/ice storm started. I don't know if it's related or not. Driving along the freeway about 30MPH because of the snow buildup, the transmission disengages, just like I'm in neutral. I coast to the side of the freeway, turn the ignition off, wait for 5 minutes, and the transmission is fine. About 10 minutes before this, the 4WD switch panel has the red LED and none of the 4WD buttons will work. I'm stuck in 2WD. Cycling the ignition does not fix the 4WD. So I drive about 1 mile in 2WD and the trans disengages again. I cycle the ignition, wait about 10 minutes and the trans works again. I repeat the process 4 or 5 times till I get off the freeway. At this point, cars are spinning out and crashing left and right. I get off the freeway and wait for 3 hours for a tow truck. I try to engage the transmission again during the 3 hour wait with no luck. I've never had a transmission problem before this.

 

The dealer reports the the transmission had a bunch of Class 2 U codes, network codes. The Transfer Case had a Encoder Motor sensor error. Trans fluid was filled, red, and not burnt. The dealer could not duplicate the transmission issue. Tuffy flushed the transmission and added new fluid 1 year ago at 110,000 miles. The encoder motor connector voltage and resistance was checked and ok. After the Dealer cleared the codes, everything has been working fine for a couple of days.

 

Now my questions.

1. If the transfer case is acting wacky, either by a bad switch, encoder motor, loose ground, whatever, should rear wheel drive still work? Is RWD dependant on the transfer case? I know the drive shaft is connected to the transfer case.

2. When a GM vehicle with Class 2 has a communication error, will the transmission still work? This is not the "reduced power mode" also known as "limp home mode" as the trans was completely disengaged.

 

Sorry for the long explanation, but I don't want to be stranded or throw a bunch of parts at it.

 

2003 Silverado, 124,000 miles, Z71, 5.3L, 4 speed automatic, 4WD push button

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the only time the transfer case disengages the rear drive shaft is when the transfer case is shifted in to neutral.

 

I have no idea how or why this could occur (on pushbutton it should not be possible to do with the truck in gear even if you pushed the buttons)

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On the switch panel, if you push 2hi and 4lo at the same time, the transfer case be put into neutral. The graphic on the panel shows a line between those 2 buttons.

 

Last night, I tried to get the transfer case into neutral using the 2 button method, but was unable. I'll look at the owners manual tonight. This would explain everything but the U codes, but those could have been previously set.

 

From another website "As far as the transfer case is concerned, when the neutral condition occurs, does the indicator show neutral? To electronically shift into neutral requires simultaneously pressing 2hi and 4lo. This specific resistance value(or volt drop) is interpreted by the module, and corresponds to the selected range output."

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If I remember right, on the 800's you have to be rolling very slowly, shift trans to neutral and mash the two buttons at the same time. I tried it once just for drill on my '05 but the thing made so much noise and clunked so loud that I never tried it again! I did have a "service 4WD" message one time with it also and they replaced the encoder motor under warranty. I traded the truck shortly after that due to lots of front drive train noise developing.

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If I remember right, on the 800's you have to be rolling very slowly, shift trans to neutral and mash the two buttons at the same time. I tried it once just for drill on my '05 but the thing made so much noise and clunked so loud that I never tried it again! I did have a "service 4WD" message one time with it also and they replaced the encoder motor under warranty. I traded the truck shortly after that due to lots of front drive train noise developing.

 

 

Hi, I have a 2005 GMC Yukon that placed itself in 4 LO a few days ago. It took a few attempts to get it back in 2 HI and luckily we were in a parking lot when it happened. After this the "Service 4WD" message was on the info bar on the dash. I took it to the local Chevy dealer this morning guy checked for codes there were none and none in history. I have read various posts on websites etc. about the encoder motor, sensor, the 4WD selector switches, and wiring harness to the transfer all being fairly common problems. Anyone have any thoughts or best course of action here? I am afraid it could happen again on the interstate or something which would be VERY BAD for the transfer and trans. The guy checked the codes from under the dash. Do the codes for the transfer have to be read off of it or is it all fed through the same port?

 

Thanks,

Aaron

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I checked the owners manual and it does list a procedure for getting the transfer case into neutral. It said you have to be parked, parking brake set, trans in neutral, and hold 2 buttons for 10 seconds. I was able to get the transfer case into neutral. The service manual did not say anything about rolling/moving.

 

I mostly took apart the 4WD switch. I did notice some dirt or something on the button contacts. I'll clean those up, compeletly take apart the switch and resolder.

 

Aaron, you can either cycle the ignition, pull the TREC fuse, or disconnect the battery to reset the system. This will temporarily fix the problem, at least it does for my truck.

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Replace the electronic sensor on the side of the transfer case. It is a little ring looking part that is inside the square box that actually changes your transfer case gears. My truck has done this off and on. Sometimes I'd be driving and it would go to auto 4x4 and sometimes 4hi. I've even had it say it was in neutral when I started truck. Cycling the key works for a quick fix but the part is only about $70 to fix it right. Don't change the dash switch out. As if you do you're wasting money. My uncle works as head mechanic for a local dealer and once I done mine it has been problem free.

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Replace the electronic sensor on the side of the transfer case. It is a little ring looking part that is inside the square box that actually changes your transfer case gears. My truck has done this off and on. Sometimes I'd be driving and it would go to auto 4x4 and sometimes 4hi. I've even had it say it was in neutral when I started truck. Cycling the key works for a quick fix but the part is only about $70 to fix it right. Don't change the dash switch out. As if you do you're wasting money. My uncle works as head mechanic for a local dealer and once I done mine it has been problem free.

 

Thanks I appreciate the help. When it went to 4 HI did it actually engage or just read on the switch panel? Reason being mine actually tried to engage 4 LO it clunked and felt like it made it into 4 LO. Just curious I am going to replace the sensor and or the whole motor either way based on your post and a few other things I have read the switch is more of an earlier year problem. The sensor and wiring harness seem to be more 04 on up issues. I will switch it out post for anyone else having the issues. Thanks again if it wasn't for places like this I would have made several trips to the dealer and probably would have had all kinds of parts thrown at it. They said they couldn't find a code so no telling where they would have started!

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  • 4 years later...

Finally, after 10 years I have found a forum that matches my issues. This should be a borderline recall issue. It has happened to me while driving, it has happened to me after the truck sits!! This has been the one problem that has haunted my '05 Sierra from day one. Just started happening again a week ago and my truck will not stay engaged in 2hi. Luckily it is defaulting to Auto 4wd. Frustrating beyond control!!!

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  • 4 years later...

I have 04 Yukon won't go into 4 low try to but times out and all you hear is grinding when it does and if I'm driving around in 2 high it slips transfer case into neutral I've tried fuses looked at wiring seem good any ideas?

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