These are Dexter axles, right? Not Lippert.
Find the Dexter Axle Service Manual at http://www.dexteraxle.com/literature1
, look for Service Manual for your axle capacity and download it. It has a page of grease recommendations, in the 800-8K LB manual look at page 53.
One of the greases Dexter recommends is Valvoline Multi-Purpose GM which is Valvoline part number VV614 in a 16 oz tube. That is what I have used for the last 28 years. It is easy to find, Advance Auto, O'Rielly, NAPA, etc.