Transmission Fluid

[Tom Wesenberg]

Since the Model A is a non-syncro tranny, gear grinding is simply a function of proper double clutching or correct timing of the pause between upshifts. Either method will depend on the viscosity and temperature of the gear oil used. I find double clutching easier to perfect than the timing between upsifts with no double clutching. Down shifting takes a lot of practice and I very seldom downshift to first while in motion over about 5 MPH.

[Bruce,Upstate NY]

When the manufacturer (STP) says don't use it straight, I wouldn't. I understand its purpose is as a viscosity increaser, not a straight lubricant.

[Louis]

Originally Posted by Bruce,Upstate NY

When the manufacturer (STP) says don't use it straight, I wouldn't. I understand its purpose is as a viscosity increaser, not a straight lubricant.

Would today's STP be better then what was used in the 30's, 40's ?

[JBill]

I've been using half 600 weight oil and half STP and have had no problems with shifting/grinding, though I haven't checked for the foaming that's been mentioned in this thread. That's just in the transmission, not in the differential.

[eagle]

I really like the "feel" of the Lucas hub oil. When you shift, the gears feel silky smooth, not the hash metel-on-metal feeling of the 600W. It is not really so thick, just really sticky so the gears are covered in it all the time. Take a drop between your finger and thumb, when you open your fingers it strings out, sticky like syrup or honey. I learned to drive in a 1950 Dodge 1 1/2 ton grain truck at home on the farm, so its not that I don't know how to shift & double clutch etc. But, Lucas makes it a lot easier, and doesn't fade when the tranny gets warmed up.

[bogiediver]

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From the Lucus Hub Oil stats page...
http://www.lucasoil.com/images/media...C99DB079CD.pdf
Viscosity @ 100°C cSt = 65.0

From a forum re: STP
Viscosity @ 100°C cSt = 250
Zinc compounds: 10%
Petroleum distillates: 30%
Mineral Oil: 60%

From another Barn thread:
600w - Viscosity @ 100°C cSt = 27

Compare to the viscosity charts I attached -

In the first - the numbers in the red and blue bars are the 'weights' as typically used - the scale at the bottom is the 'true' viscosity

Second table - Marco posted in that other Barn thread...

Ah - another oil thread...

Anyone got true viscosity stats on the other products mentioned?

[bogiediver]

Better image of chart 2

[Patrick L.]

The only 'gear clash' that I ever get is 2-3 when the transmitter is warm and it doesn't make much difference whether I wait or double clutch.. The other shifts are usually fine unless I screw up..
I just put in some of the Lucas hub oil.. It appears to be 'thicker' [ and certainly stickier] than the 600 weight [ not 600W] that I had in the box.. I haven't tried it yet,but, will post what happens.. I'm just posting now to let you know what I found when asking about this stuff.. I was told this stuff was also made for and will work fine in old transmitters and differentials [ heck, the bottle evens says so,, so,, after all,, it must be true. hehehe].. Time will tell, I guess..

[SAJ]

I recently had cause to wonder about the same things because my gearbox used to feel like treacle on cold mornings, and gears changed very well when warmed up. But after about 5000 miles, the changes could not be made as smoothly at higher speeds, and the treacly feeling when cold was gone. I had Snyders oil and 5% Molykote M55 suspension in it. I like MoS2 lubricant because it quiets my slightly noisy worn gears and acts as a boundary lubricant under severe conditions.
Anyway, I drained the oil and did a few quick tests in my laboratory at my company with stuff I had to hand and came up with the idea that I needed a lowish viscosity at lower temperatures, and something higher than usual at working temps.
This requires viscosity index polymers and I had some Moreys oil stabiliser to hand, plus the Snyders Transmission oil, and the MoS2 suspension, so I mixed 20% Moreys, 3.8% Molykote M55 and 76.2% Snyders. I am now running on this and gear changes are back to very smooth and easy, with a treacly feeling when cold.
Then I saw this thread, so went and got some Lucas Hub Oil, 85W-140 gear oil (I could not get the lighter oil H L Chauvin mentioned here in NZ) and Lucas Heavy Duty Oil Stabiliser.
Because I am leaving for Marquette very soon, I did not have time to set up proper API tests, so I just tested in a water bath at 20 and 25 Deg C and an oven at 70 deg C – because we run both constantly in our lab for polyester resin testing.
I reckon the running temp of my gearbox on the motorway is about 50 deg C, but this is a guess and I will measure it when I get back from the USA. The higher the oil viscosity, the hotter the box will run and this will, in turn, reduce the running viscosity of the oil until a happy balance is achieved.
The results are; Snyder Trans oil =A; Snyder/Moreys/MoS2 blend as above=B; Lucas 85W-140 gear oil=C; Lucas Heavy Duty oil Stabiliser=D; 50/50 Lucas C and D=E; Lucas hub oil=F. Results are centipoises measured on a Brookfield viscometer. Multiply by the oils SG (about0.9) to get centistokes
Temp. A B C D E F
20Deg C 3920 ? 1330 1112 2280 7720

25Deg C 2800 3900 2550 ? ? ?


70Deg C 194 210 72 340 180 268

This was a very quick look, so all the results are not there, but they show how a polymeric viscosity improver like Moreys and Lucas can lower viscosity loss at higher temps.
Lucas Hub oil looks good in the table, but it is interesting Lucas themselves advised against it in another post. The Lucas 50/50 blend looks OK too, and the blend B I am using also holds viscosity well.
None of this is a recommendation, because I know nothing about what is in the components. It could be that the Snyder oil in blend B already contains a lot of VI improver and I have added too much now. This is why I put in MoS2, which acts as a boundary lubricant where lubricant failure conditions could be approached. My gearbox is a bit quieter with the Moly than without too.
Plus it says nothing about foaming and other properties, and my shear-thinned old oil certainly foamed.
The working conditions in a straight-cut box are a lot less demanding than a hypoid box, and it is reported on this forum that straight STP, and steam cylinder oil worked fine for many years, so I suspect any of the above would perform OK in a Model A
Apologies for the long post. But it may prompt more input and experiences to help us all

SAJ in NZ

[SAJ]

Sorry, the table is a mess and I have not got time to fix it.
SAJ in NZ

[bogiediver]

A = Snyder Trans oil
B = Snyder 76.2%/Moreys 20%/MoS2 3.8% blend
C = Lucas 85W-140 gear oil
D = Lucas Heavy Duty oil Stabilizer
E = 50/50 Lucas C and D
F = Lucas hub oil

Temp....... A........ B........ C........ D........ E........ F........
20Deg C... 3920... ? ........ 1330... 1112... 2280... 7720

25Deg C... 2800... 3900.... 2550... ?........ ?........ ?

70Deg C... 194..... 210..... 72....... 340.... 180..... 268

[Brobrian]

Wow!
I'm not sure what all this means. I think maybe 50/50 Lucas Hub oil and Snyders 600w is the ticket. Did I get that right?
Of course, I live in SoCal where it never freezes and summertime temps are high.

[Art Bjornestad]

The working conditions inside an A box are pretty hostile as the gear face contact area is very small whereas a hypoid has a quite long contact area plus a wiping motion unlike a straight cut gear which really hits the face with quite a wallop. Hypoid use in a straight cut gear box will promote case hardening problems because of the high impact loads.

[H. L. Chauvin]

Art,

Something interesting is surfing the internet, (not only on Model A Forums), but also on other vintage car Forums, reviewing what inexperienced, novice vintage car owners have suggested to place in vintage car gear boxes with straight cut gears in gear boxes.

Reminds me of the uninformed construction worker's rubber boot gang of cement finishers, (who know absolutely nothing about ASTM Testing & Concrete Testing Laboratories), telling others that one can strengthen concrete by adding water; or even better yet, adding sugar to concrete.

Would not surprise me if one hears that a double shot of old time Croton Oil is good to add to Model A gear boxes. Can't get it anymore -- most people today never heard of it -- real potent & powerful stuff with just a few drops!

[SAJ]

Thanks for that nice tabulation Bogie Driver. I am obviously no good at making up tables!
Re mixing Snyder oil and Lucas hub oil, I would not attempt that, since we have no knowledge of what is actually in either one and Lucas oils recommended, elsewhere in this forum, not to use hub oil.
I stand corrected on over-simplifying the straight-cut versus hypoid oil matter. All I meant to convey is that oil selection is less tricky for spur gears than for hypoid. Hypoid boxes need certain EP additives to prevent localised tooth welding that spur gear boxes do not need. These gears can take more torque than spur gears due to multiple tooth contact, but the sliding action requires use of EP additives at levels not necessary in spur gear boxes. In these, the lubricant formula can be less complicated, so gear failure is less likely as long as a good gear oil is used. None of this means that a hypoid oil would be good in a Model A gearbox, however, for several other reasons.
But simpler spur gear gear oils still benefit from anti-corrosion, anti-oxidation and anti-foam additives (which I imagine were not in original steam cylinder oil) and these may or may not be compatible in different brands of oil. So I would not personally randomly mix these just to arrive at a certain viscosity.
I making up the Snyder/Moreys/MoS2 formula mentioned, I held the mix at 100 Deg C in an oven for several weeks and then filtered it to ensure no horrible interactions occurred (sludging, oxidation etc) before I used it.
This post is a bit complicated and the hypoid bit is fairly irrelevant to Model A's, so I wish i had not used this example now.
I should say that I am no lubricants chemist these days, and have forgotten much of what I knew many years ago when I manufactured oils and greases under the Rocol (UK) brand
Regards
SAJ in NZ