1941 Buick transmission

[Den41Buick]

Does anyone know the transmission oil type for a 1941 Buick? Someone borrowed my shop manual and I am unsure where to add it. Any suggestions? Thanks

[Kenneth Carr]

The manual says to use "S.A.E. 90 E. P. Transmission Lubricant for temperatures not lower than 10° F. below zero. For temperatures lower than 10° F. below zero, add S.A.E. 80 E. P. Passenger Car Heavy Duty Hypoid Lubricant."

 

I use what is commonly available, 85W-140 gear lubricant. The transmission quiets and shifts easily. I suspect plain old 90 would be better but this one works for me.

Raise the car on a pair of ramps so you can fit under it. Be sure to use chocks on the rear wheels so it won't roll back.

Get under the car on the passenger side. Find the transmission.

You will see the drain plug on the bottom. On the side is a similar plug. That is the fill plug. Remove it and then pump the lubricant in until it starts to flow back out. Now it is filled. I use a sort of hand-operated suction pump. It comes with a nice flexible plastic hose that you can insert right into the fill hole. Suck up some oil from the oil container and then pump it out into the fill hole. I have tried using a funnel but it is really difficult to to do. 

 

In the photo the filler plug is the upper square plug. Above it you can see the floorboards. The angle is a bit odd because of how

I was wedged under the car.

 

Edited August 6, 2016 by Roadmaster71
Additional info., photo, cautions. (see edit history)

[Morgan Wright]

I just get the plastic quart squeeze bottles of 90W. Tip it sideways and squeeze until the tranny is filled up to the hole. Until recently I'd have to add the whole quart but after I took my baby in to get the clutch changed, the mechanic replaced the front oil seal on the transmission, and it doesn't leak anymore. I filled it for the last time 2 weeks ago.

[27donb]

11 hours ago, Roadmaster71 said:

Raise the car on a pair of ramps so you can fit under it. Be sure to use chocks on the rear wheels so it won't roll back.

 

Transmission and rear axle oils are best checked and filled with the vehicle level.  Ramps in the front only would give too much of an angle to get an accurate level reading or fill amount.

 

When I use ramps for the front wheels, I simply jack up the rear axle also and use jackstands to position the whole car at an elevated level.

[Matt Harwood]

For the transmission, make sure it's GL4 or older. GL5 may potentially harm yellow metal in the synchros. Don't let them tell you that GL5 is backwards-compatible, because it's not in this case. I use an oil called Sta-Lube 85W90 available off the shelf at NAPA: https://www.napaonline.com/napa/en/p/SLRSL24239/

 

It's GL4 and also safe to use in the rear end. I've got it in both transmission and rear axle of my 1941 90 Series and it seems to work just fine.

[Daves1940Buick56S]

I second Matt's post. The 85W140 mentioned above is likely GL-5. Drain it out and replace with a GL-4 like the Sta-lube. The Pennzoil Syncromesh oil they sell is too light for us, it is meant for modern transmissions.

 

Cheers Dave

[Buicknutty]

Thanks for the tip, Matt. I did not know about GL4 vs GL5 gear oil.

Keith