4x4 lock out
i thought this out when every one was talking expensive solenoids, i went to my locale pet store and bought a manual two way air valve, less than $3. 00 that resembles a ball valve if you will. (the only one they had, no available). it actually has four ports on it. you use the two with the valves and plug the other two. just a 1/4 turn of the handles turns them on or off. you must use a pretty rigid walled tubing. surgical tubing will collapse. mounted it under the dash with the parking brake release handle.
one word of caution, watch the amount of torque you apply to the drive train, twice the torque when engaged, probably more than that.
just my penny's worth
Marv.