There is an id # on the old seal.You may be able to see it if you clean the seal off while still installed.Parts place should be able to ID the replacement seal from that #. 

  

Just measured mine and also came up with 1 1/2 OD on the yolk. You have the wrong seal. I am thinking he gave you the one for the heavy duty over drive transmission. It has the same size yolk as the large input Ford Toploader.

Hi,

In the process of replacing the tranny extension housing seal, where the drive shaft yoke is installed on the splined shaft.

I bought a new one from a local tbird parts store and it is tooooo big, both for the yoke outside diameter and the extension housing, so both the id and od are toooo big.

does anyone have the dimensions for the yoke, cuz i heard from some of the older builders that there were different diameters of yokes.

any help would be greatly appreciated.

ps:  my driveshaft yoke diameter is 1.50" measured with a set of calipers.

thanks

mike