That's what it is. The person that installed the pin probably drove it in too far or it is possibly undersized. You could drain the oil and try to clean the area real well and apply some gasket sealer or JB weld.
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