4X4 sometimes does not work

[Petey]

Would a lazy front axle actuator cause this problem?


My 06 4x4 has been working intermittently this winter (snowed 2x for the first time last week). When you start the truck, sometimes none of the lights on the switch light up. When you move the switch the light blinks for 30-60sec then turns off. If I turn off the truck sometimes it will work fine when its restarted other times, nothing. Last night I noticed that if you move the switch to 4hi when its not working it does its blinking thing then all the lights remain out, but when you start to slip all of a sudden the light lights and the system starts working. When the system works...its works fine and you can change the selection many times with no problem. I have never seen a Service 4WD message either.

The truck has 60k on it and I changed the transfer case fluid at 50K with the GM stuff.

Best suggestions to get a new one?

 

[The_Roadie]

There are no conditions that a bad front axle actuator would result in zero lights on the switch. It's either the switch, wiring flakiness, or the TCCM. Do you have a buddy to swap with?

 

[Petey]

No we went from having 3 360's in the family to only mine.


When the system is acting up, if I change the switch the correct light will blink (2hi, a4wd, 4hi, 4low) then nothing will stay lit. So it seems like the switch is working but not communicating with the TCCM. Have other TCCM's gone in 06's them going bad doesn’t sound too common. Any good places to look at wiring to start?


I'm hoping to avoid a trip to the stealer but it’s looking that could be what’s in store. The problem is intermittent but in the last week/3 days it’s happened over half the time, but I know it will work for them.

 

[The_Roadie]

Pull the switch out of the panel and look at the back of the switch. Disconnect and reconnect it a few times to clean up the contacts.

I assume (maybe wrongly) that you ALREADY tried to clean the switch contacts up by turning it the traditional 50-100 times CW and CCW all the way? A switch that isn't exercised is likely to get oxidized and behave that way. But a replacement switch is (now after a redesign) cheap even from the dealer.

Only the 2002 TCCM had a failure rate that was notable at all, and that communication problem would light up the "Service 4WD" lamp along with a dark switch.

I can imagine an actuator or motor problem that we haven't seen before causing your behavior. When it's working, I assume you memorized the noises made in each of the mode transitions? Does it make either of whose two noises when it's misbehaving?

 

[Petey]

Some new info that I have figured out today.


From what I can tell the system only acts up when truck sits long enough for the TCCM to go to sleep and is started in 2hi. It appears to act normal when I leave it in A4WD. If I leave it in 2hi it will blink for a bit then I have dark switch, but if I put it in neutral (transmission) then switch to any selection (2 a4wd, 4hi, or 4 low) it will "wake" up and work normal.


No there are no sounds from anything under the truck when it's dead.


The service tech told me it could be one of 3 things, axel actuator, switch, or encoder motor with his bet on choice 3 based on symptoms, but could not tell for sure without putting in on the computer. He said it's possible for anyone of the 3 to fail w/out setting a light if the TCCM receives a message from it even its the wrong signal. Onstar could not get any codes from it either.

Thanks for your assistance Roadie

 

[1978chevy4x4]

Im new tothis platform but have been fighting the exact same problem in GM trucks for several years. The TB and trucks have VERY similar 4x4 systems. I would take apart the connections to 4x4 switch, encoder, and axle actuator check their condition. Then use a contact cleaner and give em some dialectric grease. Then I would also check the body to frame ground wire(s) for tightness and clean them. I dont know there location on the TB but my truck had one under the driver door area. Also my truck only acted up when it was cold outside, I wish I fully undertood the reason for that but I don't. Hope this helps.

 

[Petey]

I checked the transfer case and the front axle actuator connections. Both looked clean and dry. I could not find any chassis grounds thought (I know there are some). The system worked great until that evening.

But I did find out some parts to the puzzle. I was incorrect in saying the switch is blacked out when the system is acting up. If fact it’s telling me, it thinks the transfer case is in neutral, (it’s tough to see that read “N” during the day) which is why it starts working when I put the transmission in neutral. I messed around with the switch for a 10 min or so switching it through all the settings including neutral.

It worked as it should for about 4 days until today, when I switched it into 4low to test it out. Now it’s acting up again (if you shut the truck down in 2hi when you restart it thinks it is in neutral). I also noticed now it’s going into neutral very slowing or not all the way. When the truck is idling with transmission in neutral, transfer case in 2 hi, if I try and put the transfer case in neutral it grinds and I quickly shut the engine off. If I switch it into neutral with the engine off and start the engine everything is fine and the transfer case is in fact in neutral.


Sounds like the encoder is hanging up and sending bad signals, unless there is another switch on the transfer case I am missing.


Oh and Roadie, can you post a link to that site that has all the parts diagrams. I thought I had bookmarked it but I must have lost it somehow.

 

[Wooluf1952]

These both have good parts break downs: GM Parts at GM Parts East | Genuine OEM GM Parts and GM Parts - Chevrolet Parts, Cadillac Parts, GMC Parts and Buick Parts powered by Nalley Buick GMC Brunswick | Nalley Buick GMC Brunswick

 

[Petey]

has anyone tried to replace just the encoder ring? Rock has one available.


I'm not really sure how the motor/encoder works, but it seems to me that its not telling the TCCM the right location information. If I turn the key to the run position when the engine off when its acting up (switch lights blinking) then put the transmission shifter in neutral I hear the motor turn a little freely then it stops but tries to keep turning (because its already in 2hi)


What is the recommendation on what motor to get. OEM or Dorman?


Or should I still be looking at the switch even though it does not appear to malfunction.

 

[Petey]

Got a new switch from the dealer and installed it. Still doing the same thing. So I'm going to try the encoder motor now. Is the doorman one worth trying? Found one online for 180.

 

[seanpooh]

RockAuto has it for $144 and you will have a 5% off with a promo code. Should be better than $180. Also, doorman does make good replacement products.

 

[plaen]

has anyone tried to replace just the encoder ring? Rock has one available.

I have, just pull the cover off of the motor, and its sitting right there, with a 3-4 pin wiring harness on it, pull the old one out, put the new one in, the ring has a groove that fits on the motor output shaft that aligns it properly, the longest part is unbolting the motor and getting the harness uncliped.

The problem I had was the ring was reporting an incorrect position when changing modes, and would cause the service 4x4 light to come on, and the entire system went dead, till the TCCM went to sleep, or I pulled the fuse.

It is possible that the ring is reporting its in the neutral position to the TCCM which illuminates the N light on the switch.

Edit: Picture of the mounting surface for reference, the two half moon shaped clips above the bolt holes are what hold the cover on.

View attachment 26508

 

[Petey]

How common is it that the motor goes? I'm thinking of getting a used one on ebay. Or should I just get one from Rock?