Silverado 4 wheel drive issues

[Robert]

Hey all,

I just started having issues with the 4 wheel drive in my truck, it seams that the front diff wont lock in. My truck is a 2004 Chevy silverado 5.3 W/manual T case FYI. I put 4 four wheels up on jack stands today, and verified that the front drive shaft is moving as it should when 4 W/D is engaged however the wheels are not. I pulled the actuator motor from the front diff and attempted to see if it was moving out of the diff, checking for weak motor. It was not, I though it might be the motor so I already ordered on and had it on hand to swap with the same results, no movement. So I checked for power at the connector for the actuator on the diff, its a 5 pin connector only 4 are have connections. The middle is ground, and the bottom left gave me 12v of power. The other two connectors gave me nothing no power nor ground. So i moved to on test the transfer case switch (the one of the T case) (manual T case) Its really tight in there so I was not able to get my leads to my DMM on the switch with out pulling it, so I tested the connector. The connector has ground in the middle and 12v on the left and right side. Not really sure where to go at this point i need a wiring diagram to verify the front diff connector but I was unable to find any so far. I attempted to ground the t case hot leads one at a time using a known good ground and a test light that did not activate the 4wd help. I also I cleaned the grounds on the frame under the drive side door just in in case.

Any one have any suggestions ?

I was thinking about pulling the t case switch, however the the nut on it is rather large and I didn’t have stubby wrench that would fit it.

So my questions.

Any one know what size the t case switch nut is?
Any one know where i can find a wiring diagram for the 4wd system ?
Is it worth getting the codes pulled some where?

Other information:

I just had the one of my front break lines burst due to rust, so I went though all the break lines replacing all of them from the ABS modal to the MC, and calipers. I only had the ground off the battery when doing so and just vacuum bled the system so there was nothing powered that was disconnected.

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Topic

[college man]

see if this helps.

http://www.justanswer.com/chevy/0u134-2004-chevy-service-4wd-the-service-center-dash-selector-switch.html

[Robert]

Thanks, but nope its a manual T-Case so no push button switch (like in the video), the switch I’m talking about is mounted to the T case and interfaces with the BCM to activate the the actuator in the front axle.

So I was able to dig up a wiring diagram

http://www.autozone.com/repairinfo/repa … cb2732#top

From my understanding of the diagram it appears that even if i grounded one side of the connector, it still would not complete the circuit to enable 4wd so my test was flawed.

[Robert]

This is more or less a bump, but I just wanted to see if some one could review the diagram and see if my though process is right.

[EricTheCarGuy]

I was able to dig this up. Perhaps it can help.

1. Disconnect the front axle actuator and check for 12 volts key on power on the Brown wire.
2. If no power, check the 4WD fuse for being blown or an open in the Brown wire.
3. Check for a chassis ground on the Black wire.
4. If OK, plug the actuator back in and probe a meter on the Light Blue wire. With the vehicle in Two Wheel Drive (2WD), there should be 12 volts there. When put in 4WD, then the voltage should go to 0.
5. If no toggle in voltage, check the Light Blue wire for an open circuit back to the Transfer Case Control Module (TCCM).
6. If the actuator is working, then remove it and try to manually engage the differential with a pry bar to see if there is a mechanical problem inside the differential.

Keep us posted on your progress.

[Robert]

Once again Eric you saved the day! Ill post back later with what i found so its out there for every one. Thank you SOOOO much!

[Robert]

So here is what happened, due to living in in the rust belt (Pittsburgh, PA), in combination with chevy using cheap material for their steel brake lines back in the early 2000’s, my brake lines rusted to the point where they leaked thus required replacement. The factory lines where all run tightly together along the frame rail, and used plastic clips to hold the lines in place, along with the factory wiring harness. After replacing the lines, using the factory clips was out of the question (most broke during removal 11 year old truck) so the wire harness was kinda left hanging there by its lonesome. I did my best to zip tie it up out of the way, also the lines along with the wiring harness were all run inside the driver side fender well. so the fender liner does a good job of containing it, or so I thought.

So First I started off where Eric said to start at the front diff actuator.

Testing the brown wire resulted in 12v, testing the black wire resulted in 0v, however no ground either….Heres where the red flag went up.
So i traced the wire back to a connector in the driver side fender well. Tested the the pins on the connector, Brown 12v, black 0v-no ground. I figured I’d test ohms 567…..
So I started pulling apart the split loom and following the wires back. That just resulted in a mess of tape, so I just followed the split loom back, it tucks under the cab right next to the cab mount.

With out the plastic clips to hold the harness in place the ground wire got pinched and damaged by the cab/cabmount, The wife came home at that point so I had to finish up and stop playing around,
I cut the black wire at the connector, soldered a new wire to it and ran it to it to a more localized ground. I only had 12ga and 18ga wire, and the ground used by the factory was 16 so i figured go larger and be safe.
Not the cleanest repair, but it was for testing, I’ll go back over it and clean it up later on. Hopefully take some better pictures to.

[college man]

Nice work. 🙂 I take it works now?

[Robert]

Yep works like a champ, gotta get it in so mud to verify though =)

[Author]

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