Transmission input shaft seal mystery, have never seen this style seal-should I replace it? Options

[reharvey]

I have a low mileage 72 trans ( 6000mi. ) that I'm converting to a side shifter. It has a front seal that is very different from the one in the 74 trans that is being used for linkage parts. The black seal in the 74 trans is usually what is found on all the cases I've dismantled. . The sealing area on the blue 72 is inset much deeper into the case and the outer surface sits a machined area not used on the 74 black seal. I'm sure the 72 trans has never been apart so it's an original piece. So, should I knock it out and use the seal that is in the gasket set?

Also got to say that it's great to take a trans apart and see everything inside looks like new!

[Richard Casto]

To do the side shift conversion you already have it pretty much apart. So I would go ahead and replace this seal (along with the others). You will find some seals that are "T" shaped (like the blue one) in that as you seat them, they will only go so far in before the top of the "T" makes contact. Most are like the black one in that they don't have the "T" top and you can accidentally push them straight through. However you do need to make sure they are deep enough that the throw-out bearing guide does not touch them. Both look to be seated correctly, but they are just different styles.

The other item of note is that your input shaft is a bit rusty. When you put in the new seal you will want to ensure that the part of the seal that rides on the shaft touches in the same location as the old. If it rides on that rusty area, you will wear it out. I would clean, polish and oil that part of the input shaft to help reduce the risk of that being an issue in the future.

Richard