from what i've read ford trucks from the same era and earlier all were supposed to run the 600W oils.and chucks trucks site had a page up that linked nearly all cases of leaks where the seals were new and correctly installed to not using the 600W oils.
As with multi visc gear lubes (and not having the manuals yet to check) we need to be carefull as some contain sulphurs that will attack brass and bronze..i have to get the 85-140 out of the tcase in my m37 for just that reason.hope it hasnt wreaked too much havoc.
here's a link to the mobil site
http://www.mobil.com/USA-English/Lub...nder_Oils.aspx
and some info on other suppliers
Additional Information:
Both Shell Oil and Texaco make lubricants that are very close to the original 600W product in both protection and viscosity - they REALLY slow down the transmission gears to make shifting as nice as an original car. The Shell product is called "Valvata" - The other is Texaco "Meropa 680". You might be interested in the following posted by Dave Bockman:
There have been many comments on steering box, transmission and rear-end lubrication using a 600 viscosity oil. Here is one more I like very much. Texaco "Meropa 680" The viscosity is 680 and it meets AGMA 250.04 requirements for gear oil. I have conducted a few non-scientific tests with this product and others and have found it to be more viscous and has better "stick" than the product sold by Vintique INC. "gear lubricant" for $3.75 per quart. (It even looks better than their black stuff!!) It is available in 35 lb. pails (5 gallons) for $24.00 (That is a little over $1 per quart). The product code is: 02342. -- Rick Black
I'll stop in at the chevron cardlock when i fuel up tomorrow and inquire about this and what they offer as well as prices.This may be the ticket for curing the leaking/grease filled steering gears on the m37's as well.
Corey