Hello to all,
I have a 2005 Suburban Z71 with 4wd issues. 150k on the clock... So here's my problem. 4wd only works when in Auto 4wd. When I put it 4wd lights don't blink, they are solid and say i'm in 4wd but no 4wd, rear wheels spin only. I put it in 4lo get all the normal clunks and puts the truck in low gear ratio but no 4wd, just rear wheels spin.Totally confused since 4wd works in auto but not in any other mode. Last summer Actuator and 4wd ECU were replaced at a shop. After having those 2 things fixed it worked fine for the summer but now being winter 4wd/4lo don't lock in. Took it back to the shop and they say need new transfer case???? but 4wd Auto works fine was my question to them. I was suspecting that ECU would be the culprit??? Any ideas?? Im stumped as I cant see the transfer case being bad when 4wd works in Auto mode. Any and help/suggestions is very much appreciated
Thanks

 

how do you know it works in auto? what was the reasoning they had for the tcase needing replaced? any codes?

 

The shop I took the truck that replaced the 4wd Ecu and actuator 6months ago(everything worked fine after that)suggested a complete transfer case replacement.
No" service 4wd" or check engine lights on,no blinking pushing buttons.
1st time...I know it went into 4wd while in auto because I was stuck in the snow/mud when I first discovered the problem. When I went through every option that was the only one when front tires kicked in and pulled out no problem. Since then I've gone to icy spots on my street(facing uphill) to test everything again and 4wd auto is the only time the truck is going into 4wd. Had son pushing from 2wd to 4hi while I was under truck. I can feel actuator doing something,pulled out of garage and in the driveway only rear wheels spinning in the snow. I'm still stumped

 

My 2003 Z71 is doing the same. Please help.