Check out the shop manual for the parts breakdown of the transmission. The bearing retainer also acts as a sleeve for the release bearing and part of the oil retention system for the front of the trans. The bearing nut/oil slinger works in conjunction with the aforementioned part. If there is damage or excessive wear there will be too much clearance between the components and oil will wick out the front of the trans. The only way to inspect these components is to remove the trans and partially disassemble it. Hope that helps. Great looking truck. Leaks are a pain!
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine