4wd Does Not Work

[dominicw]

Hello, I need some help and advise. The 4WD or 4x4 does not work. The front wheels are not puling. I tested it by lifting the rear wheels, put it in any 4WD mode, put it in drive and the front tires did not move. When I switched to 2HI or any other settings I can hear (and with my hand feel) the encoder motor on the transfer case and the actuator in the front differential moving and clunking. I lifted one of the front tires and in 2WD mode it spun free, but it would not spin (and the drive shaft linking from the differential to the TC moved) when I engaged the 4WD. I also checked the wire harnesses for the encoder motor and they are fine. I have not experienced any problems or symptoms that I read on the forums with the push button switch light indicators flashing or "service 4wd" message or stuck in 4HI or 4LO. I have read about a lot of problems with the encoder motor on the TC. My question is before I take out the encoder motor is, can the encoder motor be bad and still seem to hear it operate normally? Has anybody had these symptoms before and replaced the encoder motor and fixed it? Or does it sound like the clutches in the TC are bad or worn. The truck has 199k miles, it been in AK all its life so I don't think the 4wd has been used much.

 

Thank you for any help.

 

2001 Chevy Silverado 1500 Ext cab Z71

5.3L 199K miles

Electric push button 4WD mode switch

[bill190]

If this were my truck, the first thing I would do is get a GM factory service manual set, then check all the electrical related stuff with a multimeter per the troubleshooting instructions in those books.

 

Then if I couldn't fix the problem that way, then take it to a transmission shop.

 

But before doing that, might want to check *all* fuses (all sorts of computers and gizmos these days. One seeminly unrelated gizmo can make something else not work). Look in your owner's manual for all "fuse box" locations. How to test fuses...

http://www.dinosaurelectronics.com/Test_Fuse.htm

 

Also fat chance, but worth a try anyway... That is to "reboot" the vehicle computers. Disconnect the battery for 10 minutes, reconnect, turn on ignition and don't press any buttons in vehicle for 1 minute.

 

And check battery voltage with a multimeter. Should be 12 volts with ignition on and not started. 13/14 volts after starting and alternator kicks in to charge the battery.

 

Check the voltage inside the vehicle too. Like at the cigarette lighter. Should be about the same as at the battery.

 

(Basically I would check everything I could before taking it to a transmission shop, as they are not cheap!)