Transmission Oil

[1939 Tonner]

So I'm sure this has been asked a million times (but I couldn't find it)
Is this OK to use in my 1939 flathead 3 speed big truck?

https://www.autozone.com/motor-oil-a...art/265000_0_0

Your expertise is always appreciated.
Thank you

[Aarongriffey]

I’ve often wondered about that too. I don’t see why not.
Just to be safe I use something more like 75/140 in my old transmissions.
In souther CA straight 140 should be ok but I think back in the day 90 was used in warm weather and 80 in winter time in cold climates.

[HD Rider]

It's fine to use.
I used Amsoil 75-90 Manual Trans oil in mine.

[adileo]

It’s been stated many time here on Barn. Tranny has yellow metals needs to be GL4.

[Terry,OH]

There is no SFE weight mentioned. I would stay away from it and use NAPA SL-24238 140W GL-4

[JSeery]

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I agree, I don't see any call out of the GL rating, IMO it needs to be GL-4. I would also use a multi viscosity.

[dean333]

How about the differential fluid type....1934? Thanks

[VeryTangled]

Originally Posted by dean333

How about the differential fluid type....1934? Thanks

The Sta-Lube that TerryOH pointed out in post #5 is what I use in the gearboxes because it's GL-4. And I use it in the rears too but more for convenience than anything else. I have a '36 and a '35.

[1939 Tonner]

A big thanks to all of you!!!
I'll get some NAPA SL-24238 140W GL-4.

Something I noticed when I drained the transmission, it seemed to be filled well past the fill hole, and it seemed to be mixed with the corn head grease that I put in the torque tube. Is it possible for the corn head grease to get into the transmission? if so does that mean I'm overfilling the torque tube?

[Will D]

Originally Posted by 1939 Tonner

A big thanks to all of you!!!
I'll get some NAPA SL-24238 140W GL-4.

Something I noticed when I drained the transmission, it seemed to be filled well past the fill hole, and it seemed to be mixed with the corn head grease that I put in the torque tube. Is it possible for the corn head grease to get into the transmission? if so does that mean I'm overfilling the torque tube?

Check the rear diff fluid level. Fluid can transfer back and forth depending on the rake and gasket/seal conditions. If the trans is overfilled and the rear is low, it's all migrating forward. There will be transfer between the u joint and and trans if you don't have a sealed rear bearing on the trans.

[David J]

YES !!!!
If the grease is going forward it probably means your driveshaft seal is working .
If it is not the grease usually goes into the torque tube .

On cars the spec for filling the u-joint cavity is 4 oz .

I just use SAE 140 GL4 in the u-joint , tranny , steering gear and rear end . Works fine if your d-shaft seal is good and the gaskets are installed well .
1933 and 1934 cars .

Many seem to think packing the u-joint cavity full of grease is the way to go . The excess is either going in the tranny or rear end .

Originally Posted by 1939 Tonner

A big thanks to all of you!!!
I'll get some NAPA SL-24238 140W GL-4.

Something I noticed when I drained the transmission, it seemed to be filled well past the fill hole, and it seemed to be mixed with the corn head grease that I put in the torque tube. Is it possible for the corn head grease to get into the transmission? if so does that mean I'm overfilling the torque tube?

[JSeery]

Originally Posted by dean333

How about the differential fluid type....1934? Thanks

You can use GL-4 or GL-5 in the differential because of the lack of "yellow" metal in the rear axle. But, IMO, GL-4 is a better option because: rear axle lube can end up in the transmission, the gear type in the rear axle don't require GL-5 and it's similar to just use the same lubricant in both the transmission and differential.

[Anteek29]

[QUOTE=1939 Tonner;1990968]A big thanks to all of you!!!
I'll get some NAPA SL-24238 140W GL-4.

Yep...Is what I use also.

[Aarongriffey]

David J says he uses 140 in everything.
I checked the weather there last month and it was -20f three times when I checked.
My brother lives in St Croix Falls.
When I lived in River Falls I bought a ‘46 V8 off a used car lot when it was around 20 below zero.
After about 50 moles that day the rear end started to howl.
The local gas station had to use a blow torch to get the gear oil to drain.
I don’t see how he can even steer a car with 140 in the steering gear box.
Oh, and another thing;
If you put GL5 in a gearbox with yellow metals it will discolor the yellow metals after several years. It will NOT dissolve them in a few minutes like most people believe.

[nelsb01]

I have mentioned it before, but if you have a Tractor Supply store near you, check them out for trans and rearend oils.
They still carry the Ford tractor transmision oil-- GL-1 for Ford tractors manufactured from 1939-1952.

[David J]

Very simple answer .

I do not drive nor start them in cold weather .
Summer cars here .

The one that gets driven nowdays is a 34 phaeton .
Not a cold weather car and it actually still has the straight STP in the steering box Mike ran in FL .
That makes SAE 140 look runny .

Originally Posted by Aarongriffey

David J says he uses 140 in everything.
I checked the weather there last month and it was -20f three times when I checked.
My brother lives in St Croix Falls.
When I lived in River Falls I bought a ‘46 V8 off a used car lot when it was around 20 below zero.
After about 50 moles that day the rear end started to howl.
The local gas station had to use a blow torch to get the gear oil to drain.
I don’t see how he can even steer a car with 140 in the steering gear box.
Oh, and another thing;
If you put GL5 in a gearbox with yellow metals it will discolor the yellow metals after several years. It will NOT dissolve them in a few minutes like most people believe.

[42merc]

If you put GL5 in a gearbox with yellow metals it will discolor the yellow metals after several years. It will NOT dissolve them in a few minutes like most people believe.

This I agree with.

[Talkwrench]

Well Im bucking the trend on this one . Ive gone away from using GL4 and have started using the Penrite 85-140 mineral gear oil GL5. They have an additive which is "supposed too be" safe[ish] . Time will tell. Pretty sure Lawrie has just been using "standard type" gear oils without detrimental effects. I believe the damage come mostly when the oil becomes hot. Most of my driving is back and forth too work so thats not an issue.

[JSeery]

Originally Posted by Talkwrench

Well Im bucking the trend on this one . Ive gone away from using GL4 and have started using the Penrite 85-140 mineral gear oil GL5. They have an additive which is "supposed too be" safe[ish] . Time will tell. Pretty sure Lawrie has just been using "standard type" gear oils without detrimental effects. I believe the damage come mostly when the oil becomes hot. Most of my driving is back and forth too work so thats not an issue.

At lot of the GL-5 producers claim they are now synro compatible. I tend to not trust them and GL-4 is easy to come by. It is mild EP, which is what Ford specified and I don't care much for the smell of GL-5. I use Mercon myself (T5).

[Talkwrench]

Originally Posted by JSeery

At lot of the GL-5 producers claim they are now synro compatible. I tend to not trust them and GL-4 is easy to come by. It is mild EP, which is what Ford specified and I don't care much for the smell of GL-5. I use Mercon myself (T5).

here the GL4 is hard to come by and expensive