MAKE SURE THEY CAR YOU ARE JUMPING FROM HAS A DINKY LITTLE BATTERY!!!I jumped off a truck a couple weeks back and FRIED MY DIODE BOARD.It was pushing WAY too many amps, and I didn't realize it until the smoke was rising.Find some 4 cylinder POS to jump from, if you must..
The size of the battery should make no difference unless it was 24 volts which some trucks are.