I have just purchased a 74 Nova with a 350 engine in it. I am wanting to know what kind of automatic trans is behind it. How can I tell if it is a Th350 or Th400? :confused:

Look at the pan. If it looks like a square with one corner cut off then it's a 350.

An internet search will quickly provide pics of the pans and or pan gaskets to get a feel for the shapes.

Also, the kickdown (if it's still there) on a T350 is a cable like a lawnmower throttle, on a T400 it is electrical, with a connector on the trans and a switch on the throttle linkage.

http://www.roadkillcustoms.com/hot-rods-rat-rods/garage-shop-reference-Transmission-Identification.asp

vacume mod. is on driver side on a 400 and rear pasenger side on a 350