[mdb]

My drive to college was 850 miles on the Trans Canada highway along the north shore of Lake superior. This last school year I made that drive 8 times (6800 miles total), many of those were made in the middle of winter, -30 degrees and snowstorms. If you've ever driven along there you know you can go hours between any sort of town and there's no such thing as cell coverage.

My truck has the following stuffed behind the seat;
-tire iron, stubby wrenches and socket set
-red Tuck tape (so much better then duct tape!!!), I think the real name is Sheathing Tape
-plenty of oil
-spare belts
-spare headlight
-fuses
-gallon of antifreeze
-qt. power steering, tranny, and brake fluids
-emergency kit with tow rope, candles, hot pads, collapsible shovel
-couple flashlights
-lighters, matches
-knife, axe, machete
-!!rivet gun and all sizes of rivets!! (if your chrome trim has ever come loose at highway speed you'll understand the exclamation points, mine nearly took out a cop car coming the other way)
-Most important, go to the ATM before leaving and have a few hundred dollars cash

Luckily I've never been in a situation that I really needed any of that stuff (other then oil and lots of money for gas... and the rivet gun). The worst mechanical problem that hit me on the road was a leak in the radiator that caused some interesting engine temps and left me without cab heat.

As you can imagine, driving for 14 hours gives plenty of opportunities to glare at your gauges and listen engine noises.

EDIT: also have jumper cables, some hose clamps and a chunk of rad hose. Always regret not having a jerry can but for some reason never remember. I hate to stop for gas unless absolutely necessary, and have had a few close calls coming into the next station on fumes.

2ND EDIT: got 50' of 3/8" rope. Lots of this stuff I listed is something I saw on sale and said "I need that in my truck!!!"