Transmission / Overdrive: Gear Oils

[Old Radio Tech]

Trying to select the best transmission and differential gear oils for my 1st Studebaker, a 1949 2r5 170ci 4spd. Shop Manual says Hypoid oil in the differential and mineral oil in the transmission. But that was in 1949. Read the wiki on gear oils and now wonder about GL categories as well. Synthetic was recommended, but after researching that I think I'll stick with mineral oil. Looking for advice.

Paul

[Bud]

An SAE90 GL1 mineral gear oil is what was recommended for Studebaker transmissions originally. You can also use an SAE40 engine oil, but I prefer one of the more modern synthetic multi viscosity GL4 oils meant for use in manual transmissions. I've been using GL4 Amsoil Manual Transmission & Transaxle Gear Lube with great results in my transmission and in other Studebaker transmissions I service. Other suppliers such as Redline make comparable products for the older manual transmissions also. Bud

[RadioRoy]

The differential needs hypoid oil, but the transmission does not want hypoid oil. The components in hypoid oil attack the synchronizing rings and make the shifts "crunchy" instead of silky smooth.

[E. Davis]

I have to snicker a little every time I read these gear oil questions. When I got out of high school in the early fifties I took a job grease monkeying (now called a lubrication technician)at our local small town Chevrolet dealership. Although there was no Studebaker dealer in town we serviced a lot of Studebakers bought elsewhere. In this grease bay were two 30 gallon drums of gear lube. One 90 weight, one 140 weight. If the cars were leakers we used 140 if not than 90 went in. No one told me about mineral oil in Studebakers and the closest thing we had was ice machine oil anyway;whatever that was. There were a whole lot of Studebakers running for a whole lot of miles with the wrong lube in the gear boxes and I often wonder what ever happened to them because we never saw any of them come back to the repair shop.

[RadioRoy]

Just one more reason not to go to those "quicky" oil change places with anything older than 5 years or so.

[Bud]

Most people that own cars with Borg Warner manual transmissions use whatever gear oil they find at their local parts house never thinking about what was recommended for manual transmissions. I've had several Borg Warner transmissions rebuilt by a shop that specializes in manual transmissions and they recommend an 80W-90 gear oil for their rebuilt transmissions and they don't care about the GL number. I've run both T85 and T86 transmissions with 80W-90, SAE 40 engine oil and the newer synthetic lubes and haven't seen much of a difference. I've been using Amsoil manual transmission gear lube in the T10 4 speed in my 62 Hawk and out of anything I've used in the past it shifts the smoothest with the Amsoil lube. Bud

[DougHolverson]

Since we're talking about gears oils, can somebody point me to the old thread about what oil to use in a Dana 60 and New Process 5-speed? Thanks!

[Dan Timberlake]

1955 Chevy manual says for the manual trans either 90 mineral gear lube >> or << 90 wt multipurpose gear oil (same as the rear axle).

http://chevy.oldcarmanualproject.com/shop/1955/55csm0004.html

The same as 1942-1947.

http://chevy.oldcarmanualproject.com/shop/1942_47/4247csm009.htm

in 1958 Buick was calling for "Multi puropose gear" lube in the rear axle and manual trans

http://buick.oldcarmanualproject.com/manuals/1958/1958%20Buick%20Chassis%20Service%20Manual/01-Lubricare/image9.html

By 1976 Buick was calling for GL-5 in old style manual transmissions

http://www.oldcarmanualproject.com/manuals/Olds/1976/Service%20Manual/image4.html

My take on this is the hypoid (rear axle extreme pressure) additives that can cause damage to "yellow metals" like bronze/brass synchronizers do so slowly, over time. It is possible Manufacturers weren't even aware of the problem in the beginning and later didn't think this was a big deal.

[Bud]

The manual transmissions in newer cars use ATF, engine oil or synthetic lubes of varying viscosities with excellent results. I haven't heard of any transmission manufacturer in recent history that recommends an SAE 90 GL1 mineral gear lube for their transmissions and the new transmissions still have yellow metal synchronizers in them. NAPA can order SAE 90 GL1 gear lube if someone wants it. My recommendation is to use what you are comfortable with. Most Studebakers aren't in daily use any longer, so I don't believe there is a transmission reliability issue with any of the lubes that can be used. Bud