2500 suburban 4x4 goes into 4wd hi at 55 mph

[toppjimmy]

Ok, I am a used car manager at a gmc store. I bought a 2003 suburban 2500 lifted. I noticed at about 45 mph it goes into 4wd hi. Iam

driving it now without the 4wd switch connected. And it doesnt go into 4wd at all. We have replaced transfer case, balanced drive shaft. And have no idea why it goes in 4wd high at 45 to 50 mph.

 

Can someone help me before i am broke, My service dept is very young and inexperienced and its easier to throw parts than diagnose. thanks for any help

[Jsdirt]

Probably a short that's activating the transfer case without the button being pushed.

 

Knowing the wiring on all the GM's I've seen from '96 on, I would bet on it. Talk about cheaping out ...

[kstruckcountry]

Usually switching without command is an issue with the encoder motor... I'd scan it first though.

 

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[toppjimmy]

what would control the encoder motor

[Jsdirt]

Probably a computer. BCM maybe?

 

I want to say the switch does, but every manufacturer loves to throw a computer between the switch and the load for whatever reason these days.

[kstruckcountry]

The transfer case has its own control module. I haven't heard of many issues with them. The culprit is usually the encoder motor and it's a pretty easy fix.

 

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