2000 Blazer Shifting Into 4WD On Its Own While Driving.

Hey Guys, if someone could give me any ideas ASAP that would be awesome! i just bought a new (to me) 2001 4.3 V6 2 Door Blazer LS it has 106K on it and i was driving it home last night on the interstate, crusing around 75 MPH all of a sudden i felt a slight jolt. i look around to see my 4Hi was on! not knowing what to do i put it in 2Hi again. now it does it randomly(frequently) on its own so i took out the fuse for now... i hope it diddent screw anything up. The 4WD is still working. Thanks Much!!

Good idea on pulling fuse.
If it is the auto 4W get it on a good transmission scanner and check it out and pull codes and clear codes and see if any comes back.
Post back code.
Lot of problems with the 4W auto switches.
Check the circuit board on on it and a replacement switch if you replace it.
Also check wiring and plugins on everything.

Thank you very much MT-2500 For replying so fast. its not the Auto-4. just the standard Hi & Lo. so you suggest replacing the Switch? thats what i was thinking of trying. do you have an idea for what they run? again, thanks much!

I only said the 4W auto has a lot of switch problems.
Proper testing before throwing parts at it.
A good wiggle and tap test and ohm out test on it may show the problem
Check for codes first.
Check for bad wiring and corroded plugin.
As to the cost give you GM parts man a call.
Try for a discount.
There is list and cost on pricing.