2003 gmc sierra 1500 4 wheel drive truck kicks in to 4 wheel drive on its own while driving down the road

I have a 2003 GMC it has two buttons to use 4 wheel drive as most all do with push button controls...One is for standard highway driving with 4 wheel drive the other is for 4 wheel drive a low speeds for off road driving and conditions that need low speed less spin driving..not designed for highway use..and must be stopped to engage where 4 speed highway can be shifted on the go..hope this answers your question..good luck..

First of all...does it have push button 4x4? If so push the button that says auto or awd

SHIFT MOTOR ON TRANSFER CASE IS MOST COMMON PROBLEM. WILL NEED TO GET IT SCANNED TO BE SURE.

Have the computer scanned for trans codes, it should lead you to the problem.;

The bolts that hold everything in once out is very easy to replace. It islike removing a big turkey from the ovenwith the up most care.. The only trick is to remov the screw inside the pin holding the side gears in place which is inside the carrier housing

try selecting from nutreul or less then 3km

sounds like a bad encoder motor sensor.

there is a lock who mainteins the 4 wheel lock ,so you must change that or adjust that.

while in drive, engage the 4wd, then shift into neutral for 2 or 3 seconds, then shift back into drive. it works for my '98 ram.