2003 GMC Sierra 1500, 4.8 L, EXT CAB, 4WD - slips out of 4WD

COLORADO

MEMBER
2003 GMC C1500

Hey Carpros! Here's something to ponder BEFORE Thanksgiving Dinner 2007! Don't want you nodding from Tryptophan after gnawing on a turkey leg!

Note: I purchased (and babied it ever since) at 13K.
63K Mileage today

TWO CONDITIONS:
#1 Shift (floor shifter) into 4WD and no light on dash, proceed fwd and you're still in 2WD; shifter stays in same position.

#2 Shift (floor shifter) into 4WD, light on dash, proceed to drive and vehicle quietly slips out of 4WD; shifter stays in same position.

I rarely used 4WD to begin with except in winter. I was in a blizzard, the temperatures were nearly ungodly (the truck was at approx. 40K mileage) and during the storm it decided to disengage 4WD.

Since then, it decides to either not engage or to intermittenly take itself (without notice) out of 4H or 4L. Whenever this happens, it is without any noise / NEVER makes a sound - light goes out on dashboard, no error msg on dashboard.4WD is simply disengaged.

To the best of my knowledge, I've never driven over anything to harm the linkage arms, etc. Note: The tranny pan is protected by a skid plate on it as well.

3 Replies

2CARPRO JACK

MECHANIC
11,533 POSTS

Are we talking a manual t-case in an 03? Cool, always liked them better. If so then it most likely has a front diff actuator. These were problems for years and most likely still are. When shifted into 4wd, the motor on the front diff should engage it (you should be able to hear it) If not it is probably bad

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Friday, November 23rd, 2007 AT 8:13 AM

COLORADO

MEMBER
2 POSTS

Hey Jack -

I also prefer the positive feedback and the lack of electronics involved in my 4WD.

You mentioned I can hear the motor past the actuator engage. Sure enough, shut off the heater, radio, etc and you can pick up the feint sound.

Here's what I'm noticing:

The shifter is rather sloppy once engaged in 4H.
Ie there's 1/8 -1/4" of play once it's engaged

> Pull back towards seat, engage into 4H
> Slightly move the shifter fwd (towards firewall) &
& I can hear the motor disengage 4WD.

Now that's not to say I'm disengaging the 4H back to 2WD, instead it's playing w/the "slop" in the shifter.

What's the remedy? Can linkage be adjusted?

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Thursday, November 29th, 2007 AT 10:45 PM

2CARPRO JACK