348 348 engine rear seal

I am presently doing engine maint on my 1990 348 and purchased rear seal p/n 183581. This is different from the original two piece seal that I removed, being one piece only and enclosed in an aluminum housing. This was advertised as the latest variant but is too small a diameter ? Any ideas ? JGW

 

Ok, figured it out. One must work the seal lip to flare it enough to get it started......