Service 4WD

[rockola1971]

Typically they are shipped, removed, and reinstalled with the TC in neutral. If you look at a few stock pics (like the one I posted above) most should show that position.

Now, I don't recall on mine but I thought the middle position on the TC shaft was neutral. I could be wrong. Maybe @rockola1971 would know?

Here's a possible solution, but it would require opening up the encoder motor again.

https://www.justanswer.com/gm/4ph4u-2005-gmc-encoder-motor-position-sensor-gears-shift-transfer-case.html

With power applied(ignition key in the on position) push neutral switch on dash. (for models with auto4wd and no neutral button but have a neutral light you just push 2wd and 4wd Hi both at the same time for 10secs or longer and it will go into neutral position). Turn sector shaft on Tcase all the way right or left (your choice) and click back one position at a time while manually trying to turn front driveshaft output yoke on Tcase.(vehicle weight on wheels) When you find that you can completely turn the front driveshaft freely you are now in Neutral on your TCase and you already put your encoder motor in neutrla position earlier). Any other position and you will be essentially trying to move the vehicle by turning the driveshaft by hand (2wd, 4HI, 4LO) which is rather hard to do.

The things arent smart until you clock them properly then they always know what position they are in....until a fault occurs.

 

[InterceptorF]

Ok thanks that's for sure a problem as I did not realize there was a timing mark on that gear. I'll set that in the encoder motor to neutral and adjust the spline to match it, then put it back in and see how that helps ( if any) . Hopefully from there it will shift into 2WD so I can at least drive it. I rarely need 4WD for the Tahoe as I always drive my Yukon XL in the snow/slick conditions.

 

[InterceptorF]

I found the issue. The TREC fuse was blown - i noticed it was a 20 Amp installed , not a 30 Amp like it should have been. I pulled the battery connections, replaced it with a 30A fuse and after a day of no battery connected I hooked it back up. The selector switch LEDs work now and it showed up in 4 AUTO. I thought it was supposed to default to 2WD. Now I am not sure about the encoder motor since I molested it; because it 'feels' like the transfer case is engaging the front pinion in 2WD. I do not see any timing marks on the encoder motor gears as shown in the feed above so I most likely do not have it correct. Above 45 mph there is a strange vibration from the front axle area like the gears are spinning but not engaged to the wheels so I have ordered a new encoder motor off of eBay. It should be here today. Hopefully if I install an unmolested encoder motor it will properly work and the vibration will go away. Live and learn... I didn't know the TREC fuse was even a part of this until I watched a YouTube video on troubleshooting "Service 4WD" !

 

[InterceptorF]

I found the issue. The TREC fuse was blown - i noticed it was a 20 Amp installed , not a 30 Amp like it should have been. I pulled the battery connections, replaced it with a 30A fuse and after a day of no battery connected I hooked it back up. The selector switch LEDs work now and it showed up in 4 AUTO. I thought it was supposed to default to 2WD. Now I am not sure about the encoder motor since I molested it; because it 'feels' like the transfer case is engaging the front pinion in 2WD. I do not see any timing marks on the encoder motor gears as shown in the feed above so I most likely do not have it correct. Above 45 mph there is a strange vibration from the front axle area like the gears are spinning but not engaged to the wheels so I have ordered a new encoder motor off of eBay. It should be here today. Hopefully if I install an unmolested encoder motor it will properly work and the vibration will go away. Live and learn... I didn't know the TREC fuse was even a part of this until I watched a YouTube video on troubleshooting "Service 4WD" !

So installed the new unmolested encoder motor and now it’s fully repaired! The new encoder motor was set to neutral. I selected 2wd and it now feels correct. Lesson learned- check the trec fuse first!!!

 

[Lorentzoe45]

New here, thanks guys. Very helpful. I wanted to reply but there’s too many people to thank. I’m having the service 4x4 light come up also (among a couple other issues lol). Going to follow this thread and try the listed ideas!