I have a 1959 F100 with a 3 speed manual transmission. I need to replace the output shaft seal since I have remove the motor to rebuild. However I see there is a possibility of 3 different transmissions seal #'s I have a few casting numbers on the side, but nothing that matchs up with National Seals numbers. How do I determine what transmission my truck is equipt with?

Jordan

 

Can you get an acurate measurement of the yoke that slips into the seal? Technically it is called the universal joint flange though, not the yoke. Well, at any rate, once you know the size you can make sure you get the right seal.

 

If you can get the seal out, the number should be on the seal itself. Take it to a parts house they should be able to cross reference it. If not you can measure the OD of the input shaft (this is used for the ID of the seal) and the ID of the seal housing (this is used for the OD of the seal). With those two measurements, just about any auto place can get you the correct seal. Rock Auto is also a helpful site for seal issues.