How to change differential oil on a 1979 ranchero. Sealed back cover with some sort of feeder hose at top of housing?
The "feeder hose" is actually a breather tube for the differential to allow for expansion and contraction of fluid. To change the fluid you need to remove that cover. You want to clean out the inside of the differential case. You will need to clean the sealing surfaces of the cover and differential case before reassembly and put some good quality sealer on the mating surfaces during reassembly.