Z71 transfer case problem

[Hank70SS]

My 02 Z71 just started having an issue with the transfer case, or some sensor or switch. It goes into 4HI just fine, I can tell the front hubs are engaged. After driving a very short distance, like 1/8 mile, the message center lights up with Service 4WD. At that point the truck is still in 4HI but won't shift out of 4HI. I have to turn the engine off and restart it then it will shift into 2WD. It's the electric not manual transfer case.

Seems like there must be some sensor or switch that thinks it didn't go into 4WD. Anybody know what to look for on these things?

[Highway Star]

There are a lot of relays and solenoids in those electronic systems. Have the code read. It might tell you which one needs to be replaced.

[70goldss]

Try this.http://www.gm-trucks.com/forums/index.php?showtopic=44008&hl=sevice+4wd I personally like this site because of its information and because I own a 2004 4WD Suburban.

[Hank70SS]

I'll check out the site, thanks for the link.

[Hank70SS]

Read a million posts on problems with SERVICE 4WD and finally found one like mine. There is a sensor on the front output shaft, no doubt tells the TCCM that 4WD actually engaged and output shaft is turning. Guess I'll clean the snow of the truck and pull it in the garage. Maybe it's something simple like loose or corroded connection.

You wouldn't believe all the problems with bad dash switches and TCCM connections. Hopefully my problem is at the sensor and not the TCCM, it's located behind the passenger kick panel.

[zombie1969]

Hay Hank.You have probably fixed the problem by now.But if not try this.First see what the code is.Most likly its for the transfercase shift motor. First remove it and you will see a shaft the motor slides over.Turn he shaft manulaly with plyer or vise grips to make sure the transfercase is not internaly damaged and shifting properly.If good replace the motor.While there check for any leaks on the front dif and transfercase and fluid levels.

[Hank70SS]

No, never did fix it. I don't think there is anything mechanical wrong. It goes in and out of 4WD just fine. It'll also go into 4 LO ok. The light doesn't come until you drive it in 4WD for about 1/4 mile. Everything mechanically is doing what it's supposed to do. Like I said, seems the TCCM doesn't think it's in 4WD even though it is. That's why I think it may be the forward output shaft sensor. It tells the TCCM the front shaft is actually spinning.

[Bdubya]

http://www.chevyavalanchefanclub.com/cafcna/index.php/topic,104682.0/topicseen.html

Guessing this is your problem and the parts needed. Order them thru gmpartsdirect.com, mine came to about $88. Didn't fix mine yet, parts are waiting though.

[zombie1969]

http://www.chevyavalanchefanclub.com/cafcna/index.php/topic,104682.0/topicseen.html

Guessing this is your problem and the parts needed. Order them thru gmpartsdirect.com, mine came to about $88. Didn't fix mine yet, parts are waiting though.

That doesnt make any sence.Why repair it for 88 when you can replace the whole unit for 700.Thats how gm does it and look at them there doin great.lol.

[Hank70SS]

http://www.chevyavalanchefanclub.com/cafcna/index.php/topic,104682.0/topicseen.html

Guessing this is your problem and the parts needed. Order them thru gmpartsdirect.com, mine came to about $88. Didn't fix mine yet, parts are waiting though.

No I don't think that's it. If been through those forums, the symptoms of a bad encoder motor or dash switch are different. In all my searching I found one with the same symptoms as mine and they said front output shaft sensor.

The service 4wd light never comes on at random. The transfer case works perfectly. it will shift from 2 to 4 hi to 4 low and back no problem. I know for certain it is going into 4 wd. Light only goes on after driving for a 1/4 mile or more in 4 wd.