So I swapped manual transmission from dx to ex. Went to hook up the battery and the cables almost welded to the terminals. Check all 3 grounds, both sensors on trans. No idea what going on

Has anyone experience anything like this? Or where I should start with looking for the short?

 

Were you trying to connect the battery backwards?

The other thing that might do this is connecting the big wire from battery + to the starter to the wrong place on the starter, it should go on the terminal on the solenoid that doesn't already have a wire on it.

 

There is a large primary ground cable from the transmission to the chassis frame rail, most likely you didn't hook it up or its a bad connection

 

I figured it out. The post on the starter was loose and was shorting itself out. Fried the starter but luckily it was under warranty

 

Bam..I was just about to recommend looking hear. I'd be worried about everything else