After reading up a little bit on the GMC owners manual, it states that shifting on the fly from 2wd to 4wd can be done (I typically pull over, throw it in neutral, then switch into 4wd regardless of "shift on the fly"). BUT, as the person who was test driving my truck did, he shifted from 2wd directly to 4low, which caused the problem. According to the owners manual, the truck needs to be stopped, in neutral, and 4low needs to be activated at this point. In addition, the owners manual stated that the transfer case can go into "safety mode", which might have happened in my scenario. Not sure if this case is valid for 2001 chevy 5.3L/transfer case and tranny, this happened on my 2004 duramax.

 

hope it solved the problem, landiman

 

I'll try that tonight. Sounds hopeful. Thanks.

 

Lots of disinfo on this thread.

As pointed out earlier, use special GM fluid, not ATF.

On my 2005 Silverado 1500 -

1. First replaced the selector switch on the dash. No Fix.
2. Pulled fuse. No Fix.
3. Cleaned the grounds on the connectors under the truck. No Fix.
4. Changed the Transfer Case Motor Switch - Fix. This is an electrical component buried within the transfer case motor. You need to pull this off the transfer case, take it apart and replace the element. Its a little "donut" with a connector that lives beneath a small gear within the transfer case motor.

The part is cheap from Rock Auto or other. As I understand it, a "stealer" will replace the entire transfer case motor selector for about a grand. Replacing the part takes an hour or so.

***That was two years ago, Now the piece of crap is back to its old tricks. Some days I have 4wd, some I do not. Sometimes just shutting it down and restarting it will fix. What a junker.

 

OK Lads, here's the poop from my end....

I found the proper AC Delco part on Amazon. Don't waste your money on the DORMAN part. Mine lasted less than 18 months and I have read over and over that other guys have had the same luck. There's no sense in wasting your time or money. (Now, ask me in a few years IF the AC Delco part holds up!)

ACDelco 88962315 GM Original Equipment Transfer Case Range Select Position
Sensorhttps://www.amazon.com/gp/product/B0049OL6OW/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

You do not need to remove the forward drive shaft. The upper and lower bolt are easy. The mid-level bolt is right next to the drive shaft coupling and its difficult to get to, but it is possible. MAKE SURE that you hold that bolt slightly inserted into the transfer case shift motor housing when you re-install. It is too long to insert into that hole once the other two are in because of the drive shaft coupling. Or, just remove the drive shaft. Your choice.

There are videos on YouTube showing how to remove it, disassemble it and replace the encoder module. Its fairly easy.

I did the job in less than two hours start to finish, and that included changing the Transfer Case fluid, a phone call and a frosty pop.