I've got a 1952 Chevy 6100 dump truck I'm working on. I drained the pumpkin and got really old dirty lube. I jacked up the back of the truck and refilled it with diesel fuel and ran the truck in gear for 5-10 minutes and again drained nasty stuff. I also discovered a leak at the seal where the driveshaft enters the front of the pumpkin. It is a 2-speed rear axle. How hard is it to replace this seal and does anyone know a current part # for this seal? Thanks.