1996 Chevy Blazer keeps blowing crank fuse when starting.

It this happened after replacing th transmission, then check to see if you have pinched a wire I'd bet that you have and it 's catching between the block and trans shorting the wire out and blowing the fuse. It willprobably will be a purple wire that is pinched. here's a schematic........ click on the pic it should enlarge if you want it to.

If it startd several times before then it may still be teh same thing, onl the wire hadn't shorted out completelly. Especially if you are blowing fuses. Carefuuly look and sse if the harness is pinched or maybe burnt through by the exaust manifold and shorting there. If it is burnt through, then repair the wire and use some heat tape or header tape to protect the wire so it won't burn through or move the wire away from the exaust.