Several years ago a neighbor's son stopped by my garage one afternoon
and asked if I could help out with a
problem he was having with his "new" truck, a 1972 Chevy half ton, 4x4.
I asked him what the problem was and he told me he had been out playing
in the snow that afternoon and pulled his truck into his dad's garage
so it could thaw out a bit. Now he was wanting to take off again, but
his back brakes seemed to be locked up.

After confirming that yes, he had in fact set the parking brake after
pulling it in, I said,"no big deal,you
just need to back it up for a ways while pumping the brake and the
automatic adjusters should free it right up."

He says "Fantastic, thanks Dude!" He proceeded to improvise on my
advise by using his Dad's floor jack to raise the whole rear of the
truck off the floor and stick some cement blocks under it to keep it
there. He then started that old small-block Chevy up, adjusted the gas
pedal to about way to much, put it in reverse and popped the clutch.(I
had told him it may be a little hard to get it started off, but it
could be done...)

Since he neglected to unlock the hubs and take the transfer case out of
high-lock when he parked it, guess what happened?!

That thing shot backwards like it was launched from Cape Kennedy and
headed for outerspace, went through the overhead door since it was only
raised a foot or so, shot straight across the alley that backed our
properties and through another neighbors chain-link fence and hedge
row!

The cement blocks tore the hell out of the undercarriage, oil pan, etc.
but worst of all, Dad's brand new snowblower had "somehow" been left
laying in the driveway!

I laughed so hard I almost needed CPR to breath again! Of course he
told his Dad that he'd "..,only did what that idiot friend of yours
told me to!" But since we grew up together and raced stock cars and
go-carts for years, Dad wasn't buying that crap.

Every time the boy and I ran into each other after that for years, the
kid would look me in the eye and say,"I did too know what four wheel
drive meant!" Which always brought me to tears again.