The Stovebolt Site Forums The Shop Area Driveline SM 420 gear lube?

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

I would trust Novak's advice.

This is what they say at Novak:
"When filling your 420 with gear oil, we recommend that you select a conventional mineral oil or a para-synthetic in lieu of a full synthetic oil. Properly assembled manual gearboxes do not have the thermal strains seen by combustion engines or hypoid gears. Synthetic fluid in these gearboxes, while not harmful, is probably an economic waste.

Hypoid gear oil is sulphurized higher than transmission oil and can be mildly corrosive to the non-ferrous alloys used for synchros, bushings and thrust washers in these transmissions.

An 80W-90, API-GL5 or MT-1 rated fluid is very good. Some claim faster shifts from using a 50W engine oil in their transmission and we do not consider this to be contraindicated unless you operate your vehicle in a very warm environment."

Thanks Barrygmc, is this what you are referring to?

Name Racing SAE 50 Motor Oil
Size Quart
Part VV235
UPC 0-74130-00235-7

Name Racing SAE 60 Motor Oil
Size Quart
Part VV241
UPC 0-74130-00241-8

Thanks for sharing, as I said I am looking for advice to help decide what to use. Novak also mentions the use of 50 motor oil.

Mark

Almost every Walmart in the USA carries Quicksilver High Performance 90W Gear Lube in the boating section. It is made by Mercury for the lower unit of marine engines. Bet they carry it in Canada, too. That's what I use in my SM420 and my Eaton HO52 rear end.

Thanks Maybellene; Looks like I can get it at Canadian Tire over here. I will look into that. One thing I have noticed is the packaging seems to differ as to which side of the boarder its being sold

Mark

I got some GL-1 straight 90w gear oil from Napa the other day: http://www.napaonline.com/Catalog/C...-Oil-80w90-1-GAL/_/R-FHQ65201_0434862994 $13 for a gallon.

Agri Supply also has it: http://www.agrisupply.com/gear-oil-...medium=NaturalSS&utm_campaign=SSIDE/

As does Tractor Supply: http://www.tractorsupply.com/en/store/travellerreg%3B-ford-tractor-all-mineral-90-transmission-fluid-2-gal

Check your local farm supply stores and you'll probably find some.

I have been to both Napa and TSC over here with no luck at either. I think I will make a run for the boarder to pick some up.