4wd not working. AUTO 4wd works

[Johngodwin30]

My 2 Wheel Dr and auto four-wheel-drive work fine. Thr 4low and 4hi do not work. I am on a flat level surface in neutral when I press the button and the indicator light indicates a good shift. No warning lights. I hear the actuator shift when I go into four low and four high and 2 Wheel Dr. I drive up a steep Mountain Road. The only way to get up the road is auto four-wheel-drive. If I am in 2 Wheel Dr. rear wheels peel out if I’m in 4hi rear wheels peel out, if I am in 4lo Rear wheels peel out slower.

 

[wjburken]

If you’re getting the front axles to engage in Auto 4WD, the front differential and transfer case are shifting at least some of the time.

What actuator are you hearing?

Did you try this with Traction Control on and off?

I don’t believe you will see both rear wheels engage automatically until you pass the threshold for the limited slip differential to kick in and put power to the other wheel.

I’d get someone with a good scan tool, like a Tech-2 and see what’s going on with the system.

 

[Johngodwin30]

If you’re getting the front axles to engage in Auto 4WD, the front differential and transfer case are shifting at least some of the time.

What actuator are you hearing?

Did you try this with Traction Control on and off?

I don’t believe you will see both rear wheels engage automatically until you pass the threshold for the limited slip differential to kick in and put power to the other wheel.

I’d get someone with a good scan tool, like a Tech-2 and see what’s going on with the system.

I think I hear both actuators. I am not sure how to turn off the traction control. Sorry. I took her to Chevy Dealer who told me I needed a new transfer case $3,000 plus. I then took it to Cottman Transmission. They were really honest and didn’t know. I have not jacked it up myself and slid under it yet. So darn cold. :-(. Thanks for the advice

 

[wjburken]

What year is your vehicle?

 

[Johngodwin30]

What year is your vehicle?

So sorry. 2003 suburban z71

 

[Fless]

I also somewhat suspect the transfer case, although you may want to do some more diagnostics before springing for a T/C.

I had an issue with mine (same Auto system, 2004 with the NP246 T/C) where it worked as selected in Auto and 2hi, but 4hi ALSO worked as if in Auto. In other words, my front diff wasn't locked in in 4hi. It turned out to be the transfer case encoder motor.

I used my Tech 2 to view the commanded vs. actual mode. When I commanded 4hi, the 4hi mode light would stay lit on the switch, but the actual mode was Auto. I replaced the encoder motor and that fixed it. It could be that your encoder motor is not getting the T/C into the correct mode.

Find someone with a Tech 2 to view the drivetrain modes, as commanded and as actual.

 

[wjburken]

Your traction control button should look something like this.


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.

 

[Johngodwin30]

I also somewhat suspect the transfer case, although you may want to do some more diagnostics before springing for a T/C.

I had an issue with mine (same Auto system, 2004 with the NP246 T/C) where it worked as selected in Auto and 2hi, but 4hi ALSO worked as if in Auto. In other words, my front diff wasn't locked in in 4hi. It turned out to be the transfer case encoder motor.

I used my Tech 2 to view the commanded vs. actual mode. When I commanded 4hi, the 4hi mode light would stay lit on the switch, but the actual mode was Auto. I replaced the encoder motor and that fixed it. It could be that your encoder motor is not getting the T/C into the correct mode.

Find someone with a Tech 2 to view the drivetrain modes, as commanded and as actual.

Thanks for that. Sounds like same situation mine has. So you only had to replace encoder motor. That sounds cheaper than cracking the Transfer case open. I do need to find someone with a Tech 2

 

[Fless]

What part of the country are you in? There's a thread on here with a list of some of the Tech 2 owners.

I'd be curious to know what they quoted you for the T/C.

EDIT: does it HAVE traction control?

 

[89Suburban]

My 2 Wheel Dr and auto four-wheel-drive work fine. Thr 4low and 4hi do not work. I am on a flat level surface in neutral when I press the button and the indicator light indicates a good shift. No warning lights. I hear the actuator shift when I go into four low and four high and 2 Wheel Dr. I drive up a steep Mountain Road. The only way to get up the road is auto four-wheel-drive. If I am in 2 Wheel Dr. rear wheels peel out if I’m in 4hi rear wheels peel out, if I am in 4lo Rear wheels peel out slower.

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.