Or.....Take a little time and build a box out of plywood. That way it's protected a little bit on the way to and from. Hopefully they can send it back in your box too.
go to walmart or lowes and get a big rubbermaid container and put the trans in it and zip tie it to a half of a pallet. Make sure the top is covered or ups will send it via truck freight and it will cost a ton.
I strapped a c4 to a pallett and didnt put a cover on it and ups sent it truck freight and it cost me 300 bucks to send it from west virginia to texas!!