4wd not working. AUTO 4wd works

[Johngodwin30]

I have to drive mine in reverse for a bit and steer it hard back and forth to get the front axle to kick in.

I will try that. Good idea

 

[89Suburban]

It's not normal it is what it is lol.

 

[Fless]

If your front axle engages in Auto, and doesn't take more than a second or so to engage, the actuator and circuit should be good.

Several things to check:

Sometimes the dash (mode) switches go bad and don't have the correct resistance for the commands. They can be tested and cleaned, solder reflowed, or replaced. Here's a posting that shows how to check the various button values, and the resistance specs:

What did you do to your NBS GMT800 Tahoe/Yukon Today?

If it turns out to be the motor and if you are so inclined you can fix it, there is a gear inside that goes bad youtube has video it's been a long time since I watched it but I know there is one guy that showed how to do it. That’s cool. Hey I’d always rather spend $5, than $200..!

www.tahoeyukonforum.com

Also, there is an important ground on the driver's side of the frame rail, on the outside body mount. It's right below where the driver's door hinges are, but underneath the floor pan and behind the left front wheel. There are two ground connections there, with probably 3 wires. One of those seems to affect some function of the 4x4 system. Check and clean those grounds. They're bolts, and one of the holes in mine was stripped so I used a longer bolt and a nut.

This video shows where those grounds are at about 2:15.

 

[Johngodwin30]

All good info. Sorry I forgot to say I replaced the 4wd switches. It was so easy I had to go ahead and change it. I also sanded the wire connection so I should be getting a good ground. Sorry I left that out.

 

[89Suburban]

If your front axle engages in Auto, and doesn't take more than a second or so to engage, the actuator and circuit should be good.

Several things to check:

Sometimes the dash (mode) switches go bad and don't have the correct resistance for the commands. They can be tested and cleaned, solder reflowed, or replaced. Here's a posting that shows how to check the various button values, and the resistance specs:

What did you do to your NBS GMT800 Tahoe/Yukon Today?

If it turns out to be the motor and if you are so inclined you can fix it, there is a gear inside that goes bad youtube has video it's been a long time since I watched it but I know there is one guy that showed how to do it. That’s cool. Hey I’d always rather spend $5, than $200..!

www.tahoeyukonforum.com

Also, there is an important ground on the driver's side of the frame rail, on the outside body mount. It's right below where the driver's door hinges are, but underneath the floor pan and behind the left front wheel. There are two ground connections there, with probably 3 wires. One of those seems to affect some function of the 4x4 system. Check and clean those grounds. They're bolts, and one of the holes in mine was stripped so I used a longer bolt and a nut.

This video shows where those grounds are at about 2:15.

Tim's the fu*king man I love his GM truck vids, good dude there.

 

[Johngodwin30]

Your traction control button should look something like this.
View attachment 361844

I would be interested in knowing if your transfer case motor is operating properly and getting a signal when in 4HI or 4LO. Also curious is if your front differential actuator working properly and is getting a signal in 4HI or 4LO.

If you were able to verify that it truly is putting power to the front wheels in Auto4WD and isn’t making grinding sounds, that’s where I’d start looking, not a full transfer case swap.

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

 

[Fless]

Note that the video of the grounds shows a different transfer case motor from a later model. Not the one you have.

It's on the righthand side of the dash, if you have one. Otherwise there's a relatively square pocket to collect junk. You probably don't have traction control.

 

[Fless]

Tim's the fu*king man I love his GM truck vids, good dude there.

He does have some good, informative material. Someone you can believe...

 

[swathdiver]

Seems to me like a transfer case problem, probably electrical and not mechanical as Fless alluded to. Before you fire the parts cannon, get a Tech-2 on it for a proper diagnosis and tests.

 

[Johngodwin30]

Note that the video of the grounds shows a different transfer case motor from a later model. Not the one you have.

It's on the righthand side of the dash, if you have one. Otherwise there's a relatively square pocket to collect junk. You probably don't have traction control.

I do have the square pocket

Seems to me like a transfer case problem, probably electrical and not mechanical as Fless alluded to. Before you fire the parts cannon, get a Tech-2 on it for a proper diagnosis and tests.

good advice. Thanks