The Stovebolt Site Forums The Parking Lot Tons 'o Fun transmission and differential oil recommendations

I could not get a clear answer but, SAE 90 gear oil was suggested for both. Does this make sense?

James S

What make, year, model transmission and differential?

1952 GMC 9430 similar to the Chev 3800, 4 speed std transmission, 1 speed differential (5.14:1 gear ratio). I included pictures with casting numbers in the original post.

James S

There is a lot of talk about the oil for the old transmissions that have brass parts as ours do they say the best is to use a oil that is rated gl4 not gl5 or not gl4/gl5 . It is confusing but in our hood the oil is not available .I was thinking of using a synthetic in the transmission a motomaster from Canadian tire 75w/90 .the diff does not have brass parts so you could use something else if you wanted.

Synthetic lube in a SM-420 transmission will be a major mistake. The countergear has a lot of rotating mass, and synthetic lube is too slippery to allow the synchronizers to do a good job of matching gear speeds during shifting, particularly downshifts. Rear axles use hypoid gears that mesh with a sliding action- - - -transmissions don't, so using a general purpose gear lube with hypoid extreme pressure additives in a transmission isn't really a good idea. The synthetic lube in the rear axle won't hurt anything- - - -it might even lower the operating temperature a little. Using synthetic or hypoid-gear lube in a transmission isn't really a good idea. The 90 weight straight mineral oil that Ford specifies for their N-series tractors (8N, 9N, etc.) is ideal for a GM truck transmission.
Jerry

Thanks will have to hunt around some more or wait until the border opens up .Shipping is crazy for items like oil.

I found Sta-Lube GL4 85W90 GL-4 on Amazon. They should ship it to you for free if you have Prime (but maybe Canada is different). Here's a Link
You might be able to hunt around for that specific brand locally.
Another option is outboard lower unit lube. There are some that say they're straight mineral oil, although one I saw said it was GL-5. Not sure if that would make a difference.

Well don’t know about prime but a gallon is 38.99 which is 49 Canadian one choice for shipping is 49.00 most likely us so that is about 62 Canadian so 111 dollars and who knows if customs will want a few bucks I am going to wait a bit .Was reading and watched a few videos on u tube about the oils and it looks like a gl5 oil will be okay appears the additives attack the yellow metals when overheated and not during normal use ,the one video a fellow had a brass ring in a jar of gl4 and a ring in gl5 oil for a year and the gl5 ring looked shinny but did not decompose the ring another video of a rebuilder who has not seen a gl5 oil dammage a transmission only lack of oil or heat ect . It would be nice to have theses oil manufactures provide on label that there oil is good for brass ect. Also if anyone has had any bad results with the oil they used in these older manuel truck transmissions speak out please.

If you clicked the link I posted, it should have given you a price of just under $30. Maybe it's already converting to Canadian $ for you.

[on edit] I just checked amazon.ca and they want $50 for a gallon of the same stuff. Holy #%!*, they're ripping you guys off.
Maybe somebody can buy a $30 gallon for you in the US and mail it to you. No idea what postage would be, but would have to be less than $70.

Yea have to be carful was checking for floor patches yesterday and rock auto is usually pretty good for shipping so I now put items in the cart and with two 60 dollar floor pans shipping was about 500

Man, I thought shipping to Alaska was bad, but you guys have us beat on outrageous shipping costs. My condolences.
I thought the US was friends with Canada.

Anyway getting back on topic I am going to wait for the oil ,have to check a few more spots locally.