Question about GMC Sierra 1500
4 wheel not working no light to indicate its in 4 wheel
Your 4 wheel drive actuator on front differential is not working get new one
Posted on Jan 08, 2009
change actuator in front hub water gets in there freezez and ruber seal rips part only 120.00 bucks not hard to change beat upper ball joint take of spindle nut think it was 5/8 3 bolts in back should fall out
Posted on Jan 21, 2009
Just serviced my own 4x4 Suburban, by buying a 2nd hand encoder motor and replaced the old one, which was trashed by the winter salt. The device is prone to failure since it's made of alluminium and water has an easy time of entering the unit and trashing it.
CAUTION: Abbreviated gratuitous information of how an encoder motor was serviced. If unqualified to deal with repair, seek professional service.
CAUTION: Read at one's own risk.
To replace it, you need to crawl under the vehicle and remove the front drive shaft;
Disconnect the electric harness to the encoder motor, followed by unbolting it.
Take replacement encoder motor and install. There may be an issue with aligning the cogged cam of the transfer case to the encoder motor. If so, the vehicle's 4 wheels will need to be raised off the ground. The engine started, transmission in Park, and using a Vice-Grip® wrench gently rotate cam clockwise approximately 1/16 to 1/8 of an inch, then while set in this position, stop engine. Now attempt to align and attach the encoder motor.
After successfully attaching new encoder motor, attach its wiring loom.
Posted on Sep 01, 2009
On the full size, the front actuator is electric, not vacuum.
When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.
Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.
I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.
GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.
If I were you, I would buy a new heated actuator. They are available at most auto parts stores, and are about $90. They are also on eBay for about $55 plus shipping. These are very easy to change - just thread out the old one, and thread in a new one.
Good luck, That actuator is usually the problem 90% of time but check the fuse first in your fuse box.
Posted on Dec 30, 2009
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