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4 wheel drive problem: 4 HI does not work but AUTO 4WD does???

density

By density
in Ask A GM Technician

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density New Member

density

Posted
Posted

I have something wierd going on with my 2003 Chevy Tahoe Z71. The AUTO 4WD works better than the 4HI 4WD. When I jack it up and let it idle in 4HI three wheels spin strong at the same rate with the front driver side spining weakly. But when I put it on the ground and run it in 4HI on ice or whatever, the front wheels dont spin. However, when in AUTO 4WD the front wheels do spin and I get decent traction.

 

To illustrate whats going another way: I drive in 2WD and get stuck on purpose to test the thing and so I (1) push the 4HI button but no traction, same as 2HI; (2) put it in 4 LOW same thing no traction; (3) push the AUTO 4WD and it rolls right out like it is on dry pavement. How can this be???

 

I changed the encoder motor becuase it died and threw a code, 0374 I believe. That is now working normally, at least it sounds like it. Then the current traction problem started and the front acuater was not working so I changed that. The front diff oil was totally unhealthy, looked like that graphite grease plus there was shavings on the plug, so I changed the diff oil.

 

I am tottally out of ideas. Any help will be much appreciated. Thanks.

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

Well this a new one , instead of rambling the description and operation , I can provide that for you after work if you'd like , let me know .

Are you getting "service 4wd" message ?

What's t case oil look like ?

density New Member

density

Posted
  • Author
Posted

No codes right now. I am going to change the transfer case oil today. Maybe ill get lucky with that.

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

Well that can't hurt but it won't fix a mechanical concern ,

It weird that the frt diff is locked in auto and not in 4wd , very strange

density New Member

density

Posted
  • Author
Posted

yes it is very strange. normally i would just say the transfer case is done; but in this case it works for auto 4wd so i cant say that here. the transfer case fluid was pretty well done, almost black. so i put the new stuff in and maybe that will help to get the center to lock better. but i doubt it.

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