Muncie 4-Speed Oil

Getting ready to change the oil in my 1968 Muncie M-21 4 speed. Would like to know what brand and weight oil everyone is using or recommends.

Mark

it should be 75 w90 weight for the gear oil. Put some a synthetic amsoil in. It protects it alot better then regular dino oil. or use any synthetic. I put penzoil synthetic in my 4 speed and it works fine.
rj

corvette427 said: Getting ready to change the oil in my 1968 Muncie M-21 4 speed. Would like to know what brand and weight oil everyone is using or recommends. Mark

My M-21 leaks and I noticed it leaked more when I had synthetic (Red Line 75w-90 NS) in there. Supposedly, the molecules are smaller in synthetics, therefore getting into all the nooks and crannies better (love the smell, too). It's pretty expensive stuff to see it spotting the garage floor so I switched to Valvoline with no noticible difference in performance. The Diff has Red Line in it still. If it doesn't leak, I'd use synthetic.

JR