Chevrolet Repair: blown fuses, blown fuses, astro van

Question
my friend has an 1994 astro van in which the speedo fuse keeps blowing, which for some reason causes the van not to shift properly, we put in a new battery and a mechanic said he worked on it for three hours and still the fuse blows, help us please.

Answer
There are so many COULD BE THIS or COULD BE THAT, that it is impossible for me to even make a guess as to what your problem(s) is (are).

Whoever this mechanic is apparently has no clue as to how to go about fixing and or testing for a simple short circuit.

It could be something in the speedo circuit and or something else that is on the same fuse. Without personally performing the proper test procedures, I have no clue.