LB7: HVAC module shifts Transfer case into 4wd?

[TLKDRTYLLY]

I put an engine in a 2001 LB7 the other day. It's not my first time pulling and installing an engine in these trucks. The guy says when he uses his window switches or his HVAC controller, his transfer case switches into 4Lo by itself.. Back story: Engine came out for new main bearings and crank, truck sat in his barn for winter and most of this year. I pulled the engine, had a machine shop do short block work, I re-installed engine. Engine runs smooth, truck has no CEL other than Glow Plug control module (I didn't hook it up yet). He said it went into 4wd by itself at 45mph last night and destroyed his transfer case. I cant think of anything that would have caused that because it has to be in neutral for that to happen. Any suggestions would be good. Ben?

:screwy:

 

[clrussell]

Check the grounds on the side of the block and back of the head to the cab.. You'd be amazed what they can do..

 

[JRein]

Was it the 4wd engaging or was it that he had a bad case of pump rub? I don't see how this would happen as Windows and hvac would tie into part of the bcm. The only place I see the hvac and tcscm coming together is the ecm.

Sent from my SAMSUNG-SGH-I747 using Tapatalk

 

[Dan@PPE]

any sings of any wires being chewed by mice?

 

[TLKDRTYLLY]

Dan, I havent had the chance to look around under the dash as the customer is trying to find anything to get me to pay for it. I told him where it sat in his barn for months straight it's very possible mice crawled up there. He had it towed to another shop. They contacted me and said the only code he had in the truck was 0735. We all know what that is. At this point it's out of my hands. I've stared at schematics and didn't see anything except for on the upscale package the G203 was shared between the HVAC and transfer case switch. In the base it looked like the G203 was transfer case and the G200 grounded the HVAC. Thanks for the insight guys.

 

[Chevy1925]

if his shift collar and fork were worn out (being its most likely the old style), its very possible for the collar to have slipped forward enough to try to engage 4lo, only issue is it would have had the force to jam it in and "cause it to explode" when at speed. coming from a traffic stop is more likely. engaging 4hi at that speed will not destroy a transfer case unless he had something dieing in it already.

i dont see how anything you would have touched engine wise has anything to do with the wiring issues he is describing.

 

[TLKDRTYLLY]

if his shift collar and fork were worn out (being its most likely the old style), its very possible for the collar to have slipped forward enough to try to engage 4lo, only issue is it would have had the force to jam it in and "cause it to explode" when at speed. coming from a traffic stop is more likely. engaging 4hi at that speed will not destroy a transfer case unless he had something dieing in it already.

i dont see how anything you would have touched engine wise has anything to do with the wiring issues he is describing.

Thanks Chevy1925!