700R4 is not my favorite. Most all the newer transmissions are made from pressed sheet metal parts. Gone are the nice machined parts of the old transmissions. Pretty much cheap junk. And they do have a rash of problems with some of those parts like the sun gear shell, its a transmission with some difficult to work on parts without the special tools. The only thing it has going for it is OD.
These are a stronger better transmission
http://www.bteracing.com/So either a PG or THM400 if you want a good auto trans.
http://www.atiracing.com/products/trans/pg/supercase.htm