I’m getting ready to get some diff work done and will be replacing the gear oil.

My memory fails me, but I recall there was some recommendations of what type to use as the cheaper stuff foams ?

Any recommendations ?

I would go with something other than the cheap stuff if you do any highway running. I've had experience using Coastal before. I saw how it would throw oil from the vent hose after, and during, highway speeds. Replaced with Valvoline and no more throwing oil problem. I went so far as to cobble a little plastic jug to stick the vent hose into to catch all the oil thrown from the vent. I think the synthetics work better as far as film strength goes. I noticed a big difference in shifting my Harleys transmissions when I switched to Royal Purple gear lube in the transmission so that sold me on using it in a vehicle.