TM 10-1531, the maintenance manual for the WC series 3/4 tons recommends 90W Hypoid gear lube for the transmission, transfer and axles and the winch gears. The pto is lubed with the tranny oil. I would suspect the same recommendations apply to the 1/2 tons but I don't have a manual for them. As far as engine oil is concerned, I don't think 5W30 will cause any problems but I prefered 10W30 for my engine, thinking 5W was a little thin however the winter temps may be a lot different in Everett than they are here in Maryland.
I currently have a WC 12 and a WC 26 half tons. 80w90 or 85w90 are fine for your trans,
t-case, axles etc. Engine oil, however, is a whole other story these days. Originally
these trucks ran straight 30w non-detergent oil. If you have an oil filter you would use
straight 30w detergent oil, (30weights are for summer use ). 10w30 will work but it is a
very light oil comparatively. 10w40 would probably be best for summer use if you are going
to use multi-viscosity oil. To this you MUST ADD a zinc (ZDDP) additive, (Lucas, etc.) as todays oils have had this vital lubricant removed due to it's supposed ill effects on
catalytic converters. No zinc in the oil can mean serious cam and lifter damage in our
old flat tappet motors. I hope this helps.
Anyone have a lube chart? What do all the boxes etc take?
