I have a rebuilt '657 housing (657 and 741 seems to be often lumped together though). I installed a CR 18708 pinion seal in the housing and used an OK looking yoke. Shaft had some wear marks, but I really didn't think it was that bad.

Anyways, as I fired up the car and got the drivetrain moving I discovered that the seal was leaking, and leaking real bad, as in the gear lube was dripping out and getting slung around the floor pan, exhaust pipes, etc....in other words: major leak & mess.

I now pulled it all apart and suspect that the yoke shaft scoring is simply too deep. However, the brand new replacement billet yoke I have also appears to have some clearance between the shaft and the seal itself once I install the yoke. I had expected that the seal would fit around the shaft with some amount of 'interference', meaning that it would tightly wrap around the shaft.

So...I'm a little stumped here. I hate to button it all up only to have the leak again...am I missing something here?