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Manual transmission flush


Barry Wolk

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My 1933 Continental had trans fluid that dated from the dinosaur age. I changed it, but still had lots of trouble shifting. I added an appropriate amount of a Slick-50 product and things improved dramtically, but it's still not right.

There seems to be a glaze of old deposits from the lubricant on all the parts. I was thinking of lifting the rear tires, filling the trans with mineral spirits and running it through the gears for 20 minutes, flushing and refilling with proper gear lube.

I think that once the sticky film is gone I should get better shifting, no?

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Guest De Soto Frank

You might try putting the vehicle up on jacks, as you describe, draining whatever fluid and re-filling with Marvel Mystery Oil, then running on jacks ( in 2nd ) for a bit ( until things get warm), then let sit overnight. Run again the next day, until things are warm, then drain.

Not trying to be a smart-aleck, but does your Continental have a syncronized gear-box ?

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Guest De Soto Frank

Whatever you use, be sure to run it on the lower gears and reverse; high gear is direct-drive, and will not spin the other gears.

Speaking from 6000 miles experience behind the wheel of a 1928 Ford over the last 1.5 years, that crash-box shifts best using 600-weight "heavy gear oil", also known as "Steam-cylinder oil", still available. I use Lubriplate SPO-299.

Lighter oils do not slow the gears down as much between shifts, and require more time between shifts.

Double-clutching is necessary both on up-shift and down-shift.

Would suggest letting it drain over-night when you're draining the flushing-fluid.

Good luck !

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Whatever you use, be sure to run it on the lower gears and reverse; high gear is direct-drive, and will not spin the other gears.

Speaking from 6000 miles experience behind the wheel of a 1928 Ford over the last 1.5 years, that crash-box shifts best using 600-weight "heavy gear oil", also known as "Steam-cylinder oil", still available. I use Lubriplate SPO-299.

Lighter oils do not slow the gears down as much between shifts, and require more time between shifts.

Double-clutching is necessary both on up-shift and down-shift.

Would suggest letting it drain over-night when you're draining the flushing-fluid.

Good luck !

My 1933 Plymouth does not have synchromesh either (first introduced on Plymouth in 1935). However it does have sliding "dog clutches" and helical cut gears. Running 600 weight gear oil in it would not be a good idea.

I don't have the faintest idea what Continental suggested for use in the transmission in 1933. But I would suggest that a modern lubricant of similar weight to that originally specified should be used. It might very well be something different than the 600 weight "steam cylinder oil" that Ford used a few years earlier.

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Guest De Soto Frank
My 1933 Plymouth does not have synchromesh either (first introduced on Plymouth in 1935). However it does have sliding "dog clutches" and helical cut gears. Running 600 weight gear oil in it would not be a good idea.

I don't have the faintest idea what Continental suggested for use in the transmission in 1933. But I would suggest that a modern lubricant of similar weight to that originally specified should be used. It might very well be something different than the 600 weight "steam cylinder oil" that Ford used a few years earlier.

Hmm... another concern would be whether or not Barry's transmission has any "yellow metals" in it; if so, whatever lube used should not contain sulphur compounds, as these attack yellow metals, such as bronze & brass.

The Model A Ford transmission uses straight-cut "spur gears", no dog-clutches or the like there.

Any idea who made the tranny in your Continental, or what the original lube recommendation was Barry ? Any marks or insignia cast into the tranny case ?

The heavy gear oils are still manufactured and are used in industrial applications where there are significant sliding / wiping actions, such as the worm-drive in Elevator hoists...

Edited by De Soto Frank (see edit history)
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Hmm... another concern would be whether or not Barry's transmission has any "yellow metals" in it; if so, whatever lube used should not contain sulphur compounds, as these attack yellow metals, such as bronze & brass....

Off topic, but how many transmissions or even rear axle assemblies actually had plain bearings (bushings) made with bronze or brass? From what I can tell from the parts book, Plymouth never did. And the diagrams I see of early Fords show ball or roller bearings. If brass wasn't used for bushings in axles or transmissions what was it used for?

And then do modern extreme pressure lubricants still have additives that harm brass or bronze. I've heard that ended decades ago.

Not saying that the "don't use hypoid lubricants in old axles/gear boxes" is all wet, just wanting to know where it came from and if its still true. The usual explanation is that they attack "yellow metals". But what makes/models/years had "yellow metals" in them? And are current lubricants different enough from the early hypoid gear lubricants that even if it was once a problem is it still a problem?

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...But what makes/models/years had "yellow metals" in them? And are current lubricants different enough from the early hypoid gear lubricants that even if it was once a problem is it still a problem?

In partial answer to my own question: Apparently synchronisers in some transmissions are or were made with a phosphorous-bronze material. And apparently modern EP lubricants still have sulphur and phosphorous additives that can be harmful to those.

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The specs call for SAE 160 for summer and SAE 80 for winter.

There are a lot of Budd parts on the car. Did Budd make transmissions?

Looks like sliding square cut spur gears to me. No sign of synchronisers in there. :)

However it looks like the counter shaft runs on a bushing rather than rollers. Those bushings are probably a brass or bronze material.

If it were mine, I'd try a GL-1 (non-hypoid) 140w gear lubricant.

I guess I was taking for granted the roller construction of my 33 Plymouth's transmission as being pretty typical of the era. But with the constant mesh helical gears and rollers on the counter shaft I guess it is a bit different.

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Guest De Soto Frank
Looks like sliding square cut spur gears to me. No sign of synchronisers in there. :)

However it looks like the counter shaft runs on a bushing rather than rollers. Those bushings are probably a brass or bronze material.

If it were mine, I'd try a GL-1 (non-hypoid) 140w gear lubricant.

I guess I was taking for granted the roller construction of my 33 Plymouth's transmission as being pretty typical of the era. But with the constant mesh helical gears and rollers on the counter shaft I guess it is a bit different.

We're spoiled by Chrysler's superior engineering and the "Three Musketeers" (Zeder, Breer, and Skelton). ;)

Chevrolet used bronze bushings in their transmissions up in to the early '50s, I believe.

Ford was big on roller bearings, even in the days of the Model T.

Glad to hear it's working better, Barry...

It took me a little while to adjust to the "crash-box" in my Model A, but now driving it is a breeze, even more so with the correct heavy gear oil.

Now I just need to stop double-clutching my wife's 2000 Neue Beetle :o !

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I think kerosene has changed. Years ago we used it for cleaning and it would have some lubricating qualities but today it dries with no lubrication.

My '16 Peerless has an aluminum transmission case with ball bearings and bronze bushings and straight gears. The manual shows using 600 steam cylinder oil which I have been using for 55 years with no problem.

With my 1909 Mason the manual shows liquid grease for the transmission and rear end and it has to be filled through an 1/8 inch plug. I found by using Shell Alvania EP grease and thinning it some with 600 steam cylinder oil which is compatible, they can be filled through the 1/8 inch opening with an antique oil gun. It is a good lubricant and seems to work well.

RHL

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