Question about Cars & Trucks
Posted by Anonymous on
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Posted on Jan 02, 2017
that clicking sound you no longer hear is a relay switch behind dashboard ....aftermarket one's sold at all chain auto parts stores
Posted on Nov 25, 2008
I have the same problem. It is intermittent and sometimes shows up with service transmission message. To get rid of it just put the truck in park, press the 2 high button and shift into drive while it is still flashing. I will worry about it more when it blows up. You can drive with the vehicle showing the solid neutral and it seems to make no difference. It has to be a wake up problem between the control modules. It only happens on start up.
Posted on Sep 06, 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.
Good luck. The actuator is usually the problem 90% of time but recheck all of the wire harness just to maker sure there is no short before replacing any parts.
Posted on Jan 07, 2010
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