4wd not working. AUTO 4wd works

[Bill 1960]

Definitely needs more diagnosis before buying a new TC, that just sounds like the typical cop out response. Clearly all the mechanical bits are functional.

The front actuator is engaging in auto.
The TC clutch pack is working in auto.
The range select fork and gears are working in 4L.

All the mechanical parts work when commanded it seems.

My thought is a problem with the encoder, shift motor, or the transfer case motor lock. My understanding is in 4L or 4H the motor positions the transfer case clutch to 100% applied and then the transfer case motor lock holds that position. This mechanical lock is why the transfer case holds the clutches engaged even when parked and powered off.

I am not an expert on these but I believe the TC motor lock sounds like a prime suspect.

 

[Johngodwin30]

The part you spoke of last is not in the encoder motor correct that is the part that the encoder motor turns inside to transfer case I believe is that right

 

[Fless]

The lock circuit is in the encoder motor assy.

Might want to peruse these articles about the NVG246 system.

Theory of operation (Pete Huscher) which describes how these Tcases work:

https://atracom.blob.core.windows.net/gears/2006/2006-07/2006_07_10.pdf


Diagnosing:

https://atracom.blob.core.windows.net/gears/2006/2006-08/2006_08_08.pdf

 

[Fless]

Forgot to say that the wiring diagrams and voltages in the second link are not what your truck will look like, but the overall concept is there. For example, your reference voltage will be 5v, not 8v.

 

[MassHoe04]

I couldn’t find this button anywhere. Where should I look?

No, you are NOT going crazy! I have an 04 Z71. There is no Traction Control button. We have Limited Slip with the G80 rear differential locker.

 

[BeenChevy]

Had the same issue with my 05 Tahoe Z71. 4-hi 4-low = no go and only 4-auto would engage the front wheels in slip condition. Ended up replacing the front diff actuator which didn't resolve anything. Lifted the truck off the ground and when in 4-hi or low I could hear actuation inside the transfer case and front diff however rotating the front drive-shaft by hand the front wheels where locked and would turn however no true engagement on the transfer case. Swapped the transfer case encoder and motor to resolve. Opened the old transfer case shift motor/encoder to discover the encoder disc had taken on salt water and was severely corroded.

Before spending any money, you could try shifting into neutral on the transfer case, engage the e-brake and pull out the shift motor/encoder from the transfer case and open it up to see if maybe all you need is a replacement encoder disc or if it can be cleaned off.

 

[Johngodwin30]

Had the same issue with my 05 Tahoe Z71. 4-hi 4-low = no go and only 4-auto would engage the front wheels in slip condition. Ended up replacing the front diff actuator which didn't resolve anything. Lifted the truck off the ground and when in 4-hi or low I could hear actuation inside the transfer case and front diff however rotating the front drive-shaft by hand the front wheels where locked and would turn however no true engagement on the transfer case. Swapped the transfer case encoder and motor to resolve. Opened the old transfer case shift motor/encoder to discover the encoder disc had taken on salt water and was severely corroded.

Before spending any money, you could try shifting into neutral on the transfer case, engage the e-brake and pull out the shift motor/encoder from the transfer case and open it up to see if maybe all you need is a replacement encoder disc or if it can be cleaned off.

Great idea. Thanks for sharing your experience with me.

 

[BeenChevy]

You bet. If the motor encoder ring is jacked, it's only like $25 - $50 online. I probably could have spent only that but having already installed a borrowed new-in-box part from my uncle who just happened to have one sitting for a few years, I opted to keep the part and trading him a cheap optic site he spotted on my passenger seat. win-win

 

[Johngodwin30]

You bet. If the motor encoder ring is jacked, it's only like $25 - $50 online. I probably could have spent only that but having already installed a borrowed new-in-box part from my uncle who just happened to have one sitting for a few years, I opted to keep the part and trading him a cheap optic site he spotted on my passenger seat. win-win

I am seriously thinking about replacing the entire encoder motor like you did Rather than paying for the computer checker. It just seems like that is the problem. And the cost of it doesn’t break the bank. Worst case I would have paid for a new encoder motor for nothing

 

[BeenChevy]

True that. Also, if it turns out to be a problem with your transfer case (worst-case); You can find rebuilds with the problem solver case mod on Craigslist here for $400 - no core charge. I don't think it'd be hard to find a remanufactured one for a reasonable price.