TheOtherOne

I have a '99 Tahoe and about a month ago I was up driving in the mountains and had to put the truck in 4LO and then I couldn't get it to go out. Everytime I would press either 4HI or 2HI or Auto 4wd, I could hear and feel the axle trying to engage but it just wouldn't take. I was in neutral, going less than 2mph. After trying many times I finally just shut the vehicle off for quite awhile and then turned it back on and as soon as I tried switching it I got it back into 2wd.

Well, now I'm stuck in 4HI. I tried switching it to 4HI and it went, but then then I couldn't get it to go back to 2-wheel drive and this time all the lights on the pushbutton switch just shut off and my Service 4wd light on the dash came on. It won't even try to switch like it was before when I was stuck in 4LO.

Anyone information as to what would cause this would be greatly appreciated. I have a bad taste in my mouth from taking cars to the dealer/mechanic before and I want to try fixing it myself but have no idea where to start with this problem.

TheOtherOne

It seems this may be the encoder motor in the transfer case.

I got the following information from another message board. Does anyone know if it applies to a 1999 Tahoe?

It is very important that the mounting surfaces be clean and free of debris. The sealing

O-ring must be correctly in place on the encoder pilot to ensure a positive seal

SERVICE PROCEDURE (for 1992 S-10 Blazer 4.3W pushbutton 4WD)

To remove the encoder motor assembly:

1. Disconnect the negative battery cable.

2. Raise the vehicle and support with suitable safety stands.

3. Disconnect the electrical connection to the transfer case encoder.

4. Remove the front propeller shaft.

5. Remove the front output shaft yoke

6. Remove the encoder motor assembly by removing the (3) 8mm hex bolts.

NOTE: REMOVE ONLY THE 8mm HEX NUTS AS SEVERE DAMAGE TO INTERNAL COMPONENTS OF THE encoder

MOTOR ASSEMBLY MAY RESULT IF THE TORX HEAD BOLTS ARE REMOVED. DO NOT REMOVE THE TORX HEAD

BOLTS.

To install the encoder motor assembly:

1. All mounting surfaces must be clean and free from burrs and debris.

2. Set the sealing 0-ring on the encoder motor pilot.

Note: Check the alignment of the transfer case sector shaft with the drive sleeve in the

encoder motor assembly. The transfer case should be in 4-High (The flats on the sector shaft

vertical) for proper alignment. Rotate the transfer case sector shaft for proper alignment if

required.

3. Install the encoder motor assembly. Torque the bolts to 18 N.m (13 lbs.ft.).

4. Install the front output shaft yoke as outlined in section 7D-13 of the 1992 or 1993 S-10

Truck Service Manual (TRANSFER CASE OUTPUT SHAFT SEAL REPLACEMENT).

5. Install the front propeller shaft.

6. Connect the encoder motor electrical connection.

7. Connect the negative battery cable. Lower the vehicle.