Why would the older transmissions use different oil? Bearing material? Just asking cause I never thought about it or figured there was any difference. What about rear gear oil?
I've read that some new oils can be harmful to yellow metals. I'm thinking about using an 85w-140 for both rear diff and tranny but trying to find one that says its yellow metal safe.
If you do some searching, you’ll find just about as many discussions/arguments on the subject as you do with the ZDDP topic.
I worked in the commercial trucking industry for a numbe of years. Somewhere around 99/2000, manufacturers started recommending their own proprietary fluids in transmissions.
In the automotive world, companies like Tremec started recommending Synchromesh and Synchromax fluids in their transmissions. When GM started using Aisin Transmissions in Colorado’s they did the same thing. You’ll find the same trend elsewhere. If you look on the Valvoline spec sheet, they recommend Synchromesh for just about everything.
Here’s my guess. The GL4 and GL5 fluids have additives for hypoid and spiral cut gears that manual transmissions don’t need. The Ford oil should be fine. The older tractors used straight cut gears, plus they used the trans/ rearend as a holding tank for hydraulics. They don’t need the additives either.
The 85w-140 SuperTech gear lube is GL-5 rated but the back of the bottle also says "prevents corrosion on brass and bronze." I'm beginning to wonder if it's really going to even matter! Can someone verify that the circled plug on the attached picture is where I would fill this 1936 4 speed transmission? I'm sure the drain plug is the lowest one and am assuming the circled plug is where I would fill and probably fill just until it gets level with that hole? Thanks for the help!
"Why would the older transmissions use different oil? Bearing material? Just asking cause I never thought about it or figured there was any difference."
Joe,
My restored '36 Chevy PU has the same basic 3-speed transmission that was used in '32-'36 Chevy Master cars and pickups. The oil specified for those transmissions "back in the day" is SAE 160. Today stores like The Filling Station sell so called "600W" oil, claiming it is the equivalent of SAE 160 gear oil. Saying what follows here angered the owner of The Filling Station. Oh well. "600W" oil is not even a gear oil. It is a steam cylinder oil. Also, it is my experience in my '36 PU that while "600W" oil is more viscous than readily available parts stores gear oils it is not SAE 160.
I called Lubriplate and they have a product called SPO-288 gear oil. It is a true SAE 160 oil and my '36 shifts better with the Lubriplate than it ever has, and I've owned it since 1965. The trans in my '36 was Chevy's first attempt at synchromesh and it really wasn't ready for prime time. It has large synchronizer cone-cup end play and a very small 3rd gear synchronizer. But it's way better with the Lubriplate product than with any other oil I've ever tried. I first assembled this transmission in the 1960s when parts were still readily available for it. It has all new synchronizing parts and shift forks and the synchronizer end play is set at the exact middle of the factory specified dimension of 0.025" - 0.035".
As for the GL-5/yellow metal argument, in asking lubrication engineers I've learned that for the past several decades GL-5 gear oils have been buffered and are completely safe to use in contact with yellow metals.
Yes the plug you have circled is the fill hole. The transmission in my 1941 and 42 trucks is the same as yours for the most part. I would recommend that you fill the case to about 1/2 below the fill plug hole or else when the oil expands or you park on a hill facing downward, it will puke oil out of the front shaft housing and potentially on your clutch.
I think we all have chased the safe for "yellow metal" issue rabbit at one time. It can be confusing. None of the additives are necessary in these old gearboxes. I also use the straight 90 mineral oil "tractor fluid" from Tractor Supply that Mike mentioned in all of the differential, transfer case, and transmission cases.
Welcome to the site, and enjoy your truck! It would be great to share some pictures.
Yar, I been around the 600W oil when working on a Stanley Steamer, it's nasty stuff to get on your hands or floor. I don't think I would want it in a transmission, it took days to drain out of the gear case of the Stanley. It would be good for a steering box.
Here's a link to the 1938 Shop Manual. Here on page 3, they specify Hypoid oil for the rearend. http://chevy.oldcarmanualproject.com/shop/1938/38csm003.html On page 7 they give the specs for Transmission fluid. Depending on conditions, they specify 140, 160, Sae 90, 40 weight motor oil, and even Sae 90 blended with kerosene for winter months.
The Lube King version (Big R, Farm and Home, Farm King) of GL1 states that SAE 90 is the same as Non-Detergent 40 weight.
