• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

4wd Actuator

Installed the new encoder motor. Have 4 high, but the light is always flashing. Vehicle binds and bucks while on pavement. Put it on snow on the property and all 4 wheels are spinning. Felt a clunk and unbinding when I shifted to 2 High while on pavement. 4 low still a no go.

I had my wife operate the shift buttons while I was under the transfer case. Can clearly hear the shifting when 4 High is pushed. Nothing for AWD or 4 Low. So I have more work to do.
 
Husker6.5 said:
Yeah, start with the switch. If that doesn't solve the problem, then it's dive into the wiring harness. And remember, use only GM/AC DELCO parts to replace the switch with. Have you tried jumpering the 4LO terminals in the harness plug on the back of the switch to see if the actuator engages?
Click to expand...
Just replaced the dash switch, but it behaves the same as the old one.

Have not jumped anything, but will try.

I was satisifed I got the encoder motor replaced. Took a total of 2 hours.
 
Jumping those leads would simulate turning on the 4LO switch, but if you've already replaced the switch, that's moot. Time to start checking for continuity/resistance on every lead between the switch plug and the modulator plug, starting with the 4LO circuit. Also, be checking for any signs of rubbed/frayed/cut harness(es), obviously.
 
Last edited:
be careful jumping the switch pins. I found out by mistake that some areas of these trucks have some weird wiring! I tried to tie into my cargo lights by piggybacking off where the bulbs go in the light at the back of the cab to add some lights in the bed. as it turned out the lights would work but only be on with the switch on and the door open. close the door and they'd be off. turn the switch off and close the door they'd come back on!! I scratched my head several times on that while studying the diagram. I finally got them working by just using the truck bed as a ground instead of the ground off the cargo light bulb socket. I assume that was why there were no bulbs in the sockets to begin with, the PO couldn't figure out why they were on when the switch was off.
 
I had th same symptons of your 246 as you are having. I would look t the speed sensors. There is probably a short, likely a cracked wiring insulation. the rear sensor wiring is somewhat close to exhaust and gets brittle over time. The transfer case computer module needs to see certain speed before it will allow encoder motor to shift to 4lo. Now that I think about it, it could be related to wheel sensors or ABS system computer if not shifting into auto4wd either. Like you said, its electrical.


I ended up deleting my ABS entirely and swapping in a 241 case along with cable operated front actuator. I did like the auto-trac option of the 246 case, it saved my butt on two occasions, but I decided to start building my truck towards an overlander type setup.

Use the AC delco blue auto-trac t-case fluid and you will be surprised how much thaat binding cleans up.
 
Bowhunterbrown said:
I had th same symptons of your 246 as you are having. I would look t the speed sensors. There is probably a short, likely a cracked wiring insulation. the rear sensor wiring is somewhat close to exhaust and gets brittle over time. The transfer case computer module needs to see certain speed before it will allow encoder motor to shift to 4lo. Now that I think about it, it could be related to wheel sensors or ABS system computer if not shifting into auto4wd either. Like you said, its electrical.


I ended up deleting my ABS entirely and swapping in a 241 case along with cable operated front actuator. I did like the auto-trac option of the 246 case, it saved my butt on two occasions, but I decided to start building my truck towards an overlander type setup.

Use the AC delco blue auto-trac t-case fluid and you will be surprised how much thaat binding cleans up.
Click to expand...
Yeah I was starting to turn my focus to the speed sensors. BTW the ABS was unplugged when I bought this truck in 2010. After replacing bearings and sensors, it worked briefly then stopped and I could never figure it out. The transfer case did work for years, though eventually lost 4 low. So yeah, focus is now on the speed sensors.

Are there just two speed sensors (i.e. front and rear drive shafts), or is there a third one?
 
Last edited:
You must log in or register to reply here.
Back
Top