Rear Axle lubrication

[Ed in Maine]

When I am re-assembling the rear axle, should I pack the bearings and the gears with grease like a wheel bearing? I will use 600w when it is together. Ed

[Bob Bidonde]

Do not pack the differential gears with grease. Fill the differential with 75W140 Gear Oil.

[nkaminar]

I am with Bob on this. Fill the differential with 75W-140 or 85W-140 gear oil. The modern gear oils have additives that extend the life of the differential. The 600 W oil that is available now is not controlled in the same way as modern oils so you really don't know what you are getting. The 600 W oil that was available in 1930 is no match for the modern oils. The 600 W oil is not SAE 600 weight. There was a different rating system back in the day. Mitchell, who makes the overdrive and synchro transmissions, recommends 85W-140 gear oil.

[Ramman]

Not to hijack, but do you 2 gentlemen also recommend 85w-140
for the transmission?
Thanks!

[mcgarrett]

I'll jump in here and say that I'm using 85-140 GL4 gear oil in the rear axle and transmission without any issues.

[Curtis in MA]

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Can you mix the two?
I have 600w in both now. Do I have to drain it all and refill?

[katy]

Originally Posted by Ed in Maine

When I am re-assembling the rear axle, should I pack the bearings and the gears with grease like a wheel bearing? I will use 600w when it is together. Ed

Just wipe the bearings and gears with a light coating of whatever gear oil you're going to use when you're finished assembly.

[Kurt in NJ]

600w is steam cylinder oil, and for worm gears
the 600 series of industrial oils is for spur and bevel gears— I bought a bucket of shell omala 680, same smell and consistency as the old oils , not a concoction of???
shifts good unless below freezing, then driving a block in first is enough to warm it up

[Synchro909]

I used Penrite Transoil 250 in my gearbox and differential for years. During a recent tour of their establishment, I asked one of their tech guys about it. He said oils like that have a rating of maybe, GL1. Since then, I'm changing over to a GL5 modern gear oil in the diff.
Is there any yellow metal (bronze) in a Model A gearbox? I vaguely recall bronze bushes under the reverse idler gear. If there is, I won't use EP oil in there but there are other additives that will extend the life of the cog box without dissolving any bronze.

[nkaminar]

I read somewhere that GL4 can be used with bronze parts. But do not trust my memory and do your own research.

Followup: GL4 for transmissions with synchro, GL5 for the rear end. See https://www.widman.biz/uploads/Transaxle_oil.pdf

That article goes into extreme detail on the two ratings. It says that the additive in GL5 protects bronze synchro rings but that it sticks too well and instead of wearing off it peals a little of the underlying bronze. The current additive does not attack (dissolve) the bronze as the older additives (30 years ago) did.

GL5 and GL4 have the same additive but GL5 has twice as much.

The way the additive works with the steel gears is to add a protective layer that wears instead of the steel.

The GL5 is probably OK for bronze bushings that don't have the extreme impact that synchro rings do.

[mcgarrett]

I also read that GL4 is fine for yellow metal in transmissions, but encourage you to confirm that for yourself.

[Bob Bidonde]

Ditto nkaminar's posts. He is right-on!

[alexiskai]

Thanks Neil, I'll file this away for when my '39 transmission goes in.

[LeonardS]

Texaco Meropa 680 for transmission and differential.

[Patrick L.]

Grease ? Grease only goes in the outer axle shaft bearings.

[Bob Bidonde]

In 1932, Ford went to SAE lubricants. here is the service bulletin. It does not specify 600 for anything!

[Kurt in NJ]

and they went to transmission with synchronized 2,3 gear that changed lub requirements

[Bob Bidonde]

The technology to tailor gear lubricants in the 1930s was not up to specializing it for syncromesh gears. Dealers used the 1932 lubricants for all cars in their shop including Models T, TT, A, AA, B, BB & 18. 1932 was the first year Ford went to SAE rated / standardized lubricants instead of its own home brews.

[stevemclark]

Back in the 70's I used this in all things that called for 90w gear oil so I used it in the steering box,transmission and differential with no problems.85w-140w Super Tech oil from Walmart $5.66 a quart,$19.28 a gallon.