Suspect My 4wd Actuator/encoder Failing

TedH · May 30, 2008

My 'Service 4WD' light came on last night. In past experiences, all I had to do was cycle the 4WD unit on/off (from 2WD to Auto and then back to 2WD) to clear it up. Well, this time, when I tried that, it stayed in Auto. Then, when I pulled into my driveway, the truck actually slowed down when I was turning... as if it was straining. Granted the road was dry and it isn't snowing outside (end of May here in OH) so I suspect the tires were acting like 'brakes' as they were being driven slower than the rear tires....

Anyway, once I had the truck in the garage, I shut it off, turned on, tried to shift it out of Auto. Wouldn't go into 2WD but when I selected it, it went into 4HI... then it stayed there (I could not change it). Shut it off, turned on and then got it into 2WD. But, at this point, the truck sort of lunged forward like it was 'hung up' in that 4WD setting and it released the front wheels (finally). That leads me to believe it is the 4WD Actuator/Encoder that is 'hanging'.

If I buy the replacement part, should I expect my Chevy dealer to install it? I've heard the dealer prices are over $400 PLUS installation labor but saw a post where the part is listed under $100. With the price of fuel, I'd rather pay $100 than $400 (well, even if fuel was cheaper, I'd rather not be reamed by GM). I may replace the dash switch assembly also.

I'm fairly mechanical as I've performed most of the mechanical work on my 69 and 80 vettes and several motorcycles. The Silverado is out of warranty (54K miles on odometer).

Also, in case it is relevant, I just returned from a 1,250 trip to Missouri... I used 2WD the entire trip; never 4HI or AUTO. But some stretches of I-70 in OH, IN, IL and MO were pretty rough (the winters ruin the asphalt here).

Never any signs of fluid or oil leaks under the truck but I'll check the transfer case fluid/lubricant level. If it is due, I'll drain/fill also. Will also see what lubricant is recommended.

I also have a new Chilton's repair manual that I'll be studying this weekend in event this is something I can address on my own. I have a very good repair shop locally that can do alot of heavy repairs. They may get my business over a dealer; I've not had good luck with Chevy dealer service dept's.

Thanks for your input!

NOTE: I won't be driving the truck until I've resolved the issue. I've dusted off the C3 ('80 vette) and will be using it for short trips this weekend... sort of nice to 'have to' drive the C3... I've neglected it of late.

TedH · May 31, 2008

I found the 4WD Actuator at Rock Auto for $76.99. Part # is 600101 and manufacturer is 'Dorman'.

Also, found it at GMpartsdirect.com for $92.57... I'm assuming genuine GM?

Has anybody replaced this item? Easy, hard, instructions? I can put the truck on jack stands if necessary to provide clearance. If it can be done, I'd rather perform the replacement/repair myself. I can also diagnose the actuator. I noted there were posts on another forum about testing the 2-3 wires that connect to it as well as checking the fusebox.

sundawg · May 31, 2008

Hi

I have replaced mine in my 99 chevy. It is very easy and straight forward to do. Just unplug the wires and it unscrews from the front pumpkin.

Hammer2785 · May 31, 2008

It could also be the switch itself. Very common issue with these trucks.

TedH · June 1, 2008

Thanks for the info on the switch and actuator replacement. Will take a closer look at both today.

BigSilver · June 12, 2008

Hi Ted,

I've got a similar dilema with my 2003 Chev Burb. and have been surfing the net for info on installing a replacement encoder motor. Google the term "encoder motor install".

Based on my research thus far, one could try the following:

Disconnect the battery and let the electronic control module (ECM) capacitor discharge for half an hour+, then reconnect and try switching to 2WD with the dashboard buttons. If it works, great.

If not, then disconnect the battery, remove the encoder motor, and determine if you can rotate the transfer case's (TC ) cam, with a wrench, into 2wd. Which way you ask? Well that answer I am still searching for too; maybe a local tech can chime in on that one. If you find you cannot rotate the cam, try turning by hand the drive shaft, to unload the TC / drive train torque, and then try rotating the TC cam. If it doesn't move then there is a possibility that the TC is damaged, thus requiring a tear down.

As for reinstalling a replacement encoder motor (EM), I understand that rebuilt EM's are pre set to neutral. So one would need to adjust the TC accordingly before attaching the replacement EM. Then its a matter of starting the vehicle and letting the transfer case control module (TCCM) registering with the EM.

Ted, if you find out more details, please let us know.

BurbanZ71 · August 16, 2008

I think I might be doing an encoder motor soon. The service 4wd message comes on every time I start the Burb.

Since the message has come up the lights in the switch are very intermittent. The switch now says either 2wd, N or nothing at all. I had a GM mechanic scan for codes, he said the switch should be good, most likely the encoder motor. But could also be the transfer case itself.

I did pull the 4wd fuse for a couple hours but that did not good.

Any tips on how to replace the encoder motor? Any gotchas to look out for in the process?

thanks!

alex.mitchell22 · April 17, 2011

Had the same problem with my 06 crew cab. Service 4x4 came on and sometimes the lights on the switch would be off or in nuetral or in 2hi. Cranked up truck after it had been sitting for a day and everything was fine. Drove five miles and service 4x4 back on again. Took to dealership and they said encoder motor fail and replaced it. My truck hs been fine for 75,000 miles or more and now it's doing the same thing again. The onlything different this time is that the truck doesn't change by itself into 4x4 low when i change into drive. I wonder if maybe the crankcase fluid needs to be changed and thats why this problem has occurred again. Any ideas?