comments:
The crud is likely from previous use of a hub attachment. Quite often, stuff gets ingested from the attachment (usually the meat grinder, but often other stuff), ends up inside the housing, and then dries. It'll clean up. The slipping under load is usually a failed worm follower gear, but could be a cracked pin (which goes through the driveshaft, visible after you remove the snap ring and the upper bevel gear). (Also possible but less likely is the main gear worm spinning on its shaft under load.) For snap ring pliers, the Vise-Grip convertibles from Amazon are inexpensive and fit for purpose: https://www.amazon.com/VISE-GRIP-Convertible-Pliers-2-Inch-2078900/dp/B000JNRR0Y/ If you're planning to work on a lot of these, invest in a pair of Knipex 49 21 A01.