Question about 1999 Chevrolet Silverado 1500
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Posted on Jan 02, 2017
Having the same exact problem but with my 1999 escalade. Thought it was the actuator bought a new one installed it transfer case would engage but front end wouldnt lock. Took it out of housing left it plugged in got a friend to go through all the 4wd for me and the plunger never moved out the actuator. Checked my wiring harness which is a four prong ann it had one hot prong like it is suppose to. Traced wires even replaced dash switch same problem. Taking it to local dealership tom to have it checked for codes. I was told it could be the transfercase actuator even though its workin that actuator is what sends power to the front to engage the actuator to lock the differential.
Posted on Sep 16, 2009
SOURCE: I have a 2002 Chevy
Fuse is located at the end of eh dash on drivers side and the Actuator is located at the front differential and on the passenger side.
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. The actuator may not be fully engaged or disengaged and the fork to the spline may be what is causing the grinding.
88-UP C/K ACTUATOR UPGRADE
VEHICLE SERVICED: 88-99 CHEVROLET FULL SIZE
PURPOSE: IMPROVE AXLE CONNECT ENGAGEMENT TIME AND
SYMPTOMS: NO FRONT DRIVE AXLE ENGAGEMENT WHEN SHIFTED INTO 4X4.
Obtain the following GM part numbers:
(1) 26060073 Actuator
(1) 88959465 Harness/Spacer Kit
Posted on Feb 03, 2010
Several things could cause
this since it is auto 4wd and controlled by a COMPUTER! Start the simplest, cheapest troubleshooting first; the electrical and computer system contact plugs and points.
1. it could be cracked solder connections inside the push button switch - try to re-solder or replace the switch.
2. possibly the encoder motor is bad. It is on the side of the Tcase and turns a shaft to shift the case. - try getting one from a scrapyard and swap it, much cheaper than new.
3. The computer module failed, or the contact from the plug to the plug pins is corroded. - first try to unplug and plug back in a few times to make a good contact. if that fails to work, get a used one from the scrapyard and swap it ($50 compared to a new one $500!) Get some cleaning\lube spray from Radio shack for computer terminals to keep from corroding.
4. It could be that you just have a bad connection in the 4wd wiring system. That was my case, it was just the plug connection at the computer module and has been working ever since, and now I have a spare computer module sitting on the workbench.
The computer module is the biggest pain to get to. It is buried in the dash behind the headlight and push button 4wd switch. Good luck!
Posted on Jul 05, 2010
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