My brother has an 01 ZR p/u w/ electronic transfer on the dash ,the lights on the dash blink like a pinball machine and has dropped into 4 low at highway speed resulting into a Nascar spinout . When you start the truck it goes into 4low by itself . I didn't think it was possible to get to 4 low w/o putting the truck into neutral . Anyone have a clue ? No check engine light .

 

There are some other post about this around it sounds like either a really messed up control, or a vacum line is off somewhere.

 

My blazer was going into 4 wheel around 50-55 but only on the right side. All it did was make a lot of noise. I think it was something with the vacum though and the little ball.

 

I WOULD THINK GOING INTO 4 LO @ 65 MPH, THERE WOULD BE MUCH MORE TO FIX THAN WHAT CAUSED IT TO DO THAT.

 

Ditto on that...besides the fact that it sounds like a potentially fatal problem (to your truck AND you)...

 

I would pull the 4wd fuse before you drive the truck anywhere.