Hello;
I have recently cleaned out and put new gaskets and seals on my Muncie 4 speed for my 52 9430 GMC. I have read several posts on this forum and others regarding the use of proper oils in synchromesh transmissions. I have read that you should not use Hypoid oil or GL5 oil due to sulphur content affect the yellow metal in the syncros. I have been trying to find a SAE90 GL4 gear lube with no success here in Canada with no success. I see lots of 80W 90 GL4,GL5 rated oil but am hesitant to but it due to the GL5 rating. Novak actually make a statement that GL5 is ok which has confused the issue
http://www.novak-adapt.com/knowledge/sm420.htm

Any advice would be greatly appreciated.
Thanks
Mark

1952 GMC 9430 one ton pickup, a work in progress

1952 1-ton pictures on Photobucket