Transmission Oil
 

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

Re: Transmission Oil
 

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.

Re: Transmission Oil
 

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

Re: Transmission Oil
 

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

Re: Transmission Oil
 

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

Re: Transmission Oil
 

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.

Re: Transmission Oil
 

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

Re: Transmission Oil
 

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.

Re: Transmission Oil
 

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?

Re: Transmission Oil
 

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.

Re: Transmission Oil
 

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 .

Re: Transmission Oil
 

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.

Re: Transmission Oil
 

[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.

Re: Transmission Oil
 

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.

Re: Transmission Oil
 

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.

Re: Transmission Oil
 

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 .

Re: Transmission Oil
 

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.

Re: Transmission Oil
 

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]:rolleyes: . 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.

Re: Transmission Oil
 

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).

Re: Transmission Oil
 

here the GL4 is hard to come by and expensive :rolleyes:

Re: Transmission Oil
 

Rob, I too use the Penrite 85-140 gear oil.
They are a well respected Aussie company that have for years produce oil specifically for veteran, vintage and classic vehicles. I spoke to their tech guy about this and they claim it is safe for our Ford V8 boxes. I pulled my 38 gearbox apart after 2000 miles, looking for a noise which I have never tracked down. The oil was clean and the bronze bits were unmarked after 2 years using the gear oil.
Good enough for me.
Dave

Re: Transmission Oil
 

After Jseery’s post that reminds me of the time I drained everything on my Ford Aerostar.
I put gear oil in the five speed transmission.
The next day I had a hell of a time shifting it.
I looked up the specs and it said to use ATF! I changed it to ATF and it was just fine for the rest of the years I had it.
Aerostar five speeds had T5 trannies in them. I always liked the gear ratio spacing in that vehicle.

Re: Transmission Oil
 

Well thats good to know Dave. I dare say in a few years the box will be apart again for some reason.. That will be a good test. I prefer the way it shifts too, will be better in winter.

Re: Transmission Oil
 

I am in the process of purchasing a 1933 pickup. I have an instruction book for 4 cylinder cars and trucks. It says to use SAE250 in the summer for transmission and rear axel. All I can find advertised is synthetic. Any thoughts on this? I would rather ask a stupid question than do something stupid

Re: Transmission Oil
 

The call outs for lube was evolving during this time period. If you look at the Ford specs in the late 30 and into the 40s they are recommending want is now GL4. You could also use GL1.

Re: Transmission Oil
 

Nothing wrong with synthetic.

Re: Transmission Oil
 

Here is a piece I copied off a different forum, explains things pretty clearly. Note that it applies only to Valvoline's High Performance lubes, they have others that may not qualify.

In that same thread, it was stated that the active sulphates in other GL-5's only corrode/discolor brass when oil temps are in the 250°+ range, not something I'd expect in an old Ford.

Re: Transmission Oil
 

Re: Transmission Oil
 

Anybody using #30 motor oil in their standard transmissions? Thats what I have in the four speed T17 in my IH Loadstar. The manual calls for straight mineral oil #50 so this is a little lighter than they recommend. Seems to work great.

Re: Transmission Oil
 

Not at all; Lucas is GL 4/5 and very reasonable

Re: Transmission Oil
 

Here is the comparison between the different viscosity ratings. But keep in mind that the additives are very different between them.

Re: Transmission Oil
 

So according to the chart my #30 motor oil is close in viscosity to an #85 gear oil.

Re: Transmission Oil
 

Yep, but again different additives.