Left rear axle gear oil seal replaced in 2013 along with bearing;leaking again?

There is a repair kit available but need to know what size rear differential ring gear on this 1 ton van OR at least the engine size will help... Rear disc or drum brakes??..More details!... It may not even be gear oil leaking out!!!!

Sounds like a simple problem. If the bearing did not score ( Make a crease line ) in the axle the axle and seal should be fine. Check on top of the axle house there will be a hose that goes to no where, it is a vent tube. Make sure that is not blocked if it is will build up pressure in the differential assembly and make leaks anywhere. Good Luck