I have a 66 F-100 that the PO put a 390 FE and C6 transmission into.

I replaced the seal at the extension housing on the trans. where it meets the driveshaft slip yoke with TIMKEN 5203 seal. I believe it is the correct seal for this transmission and seems to fit nicely. However the driveshaft slips into this seal, and drips transmission fluid at this point of contact where the rubber meets the slip yoke. It is as if the seal is too loose because the slip yoke on the driveshaft is too skinny, or the hole in the seal is too wide a diameter. Keep in mind that the C6 is not original but the driveshaft seems to be original.

Is there a tighter seal available, or a way to thicken the spline on the driveshaft with some sort of sleeve?

On first glance it seems to fit snugly, but not really tight enough I guess.

This is the second TIMKEN 5203 seal I tried . . .

Thanks.

 

Im thinking it may also be the bushing in the extension (tail) housing?

 

The bushing develops burrs, if not replaced, can tear the new seal once it's pressed into the extension housing.

 

The bushing is new. It seemed very tight against the slip yoke so we sanded the inside of the bushing with a mandrel type sander to give the yoke more room. Maybe it got messed up doing that. Any idea how tight the yoke should be when it slips into that bushing? We were afraid of it binding it was so tight.

 

Upon closer inspection after a test drive today I've determined that the fluid is not coming out from between the rubber seal, and the yoke. It's dripping from betwen the metal flange of the seal, and the end of the housing. Maybe the seal did not go in perfectly straight - well I know it didn't, so maybe that is it. Can I use some sealant or gasket seal when I put the next one in, or does it have to go in dry?