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48 P15 fluid


woodrow

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I have a 1948 Plymouth Special Deluxe Sedan with a 3 speed on the wheel.  It has a 218 23 inch block 6 cylinder. Its all original so nothing has been altered requiring original servicing needs to change.  I am after searching the forum for an answer as to what fluid to put in the " trans" but I cant come up with a definitive answer.  I've actually come up with alot of different opinions but cannot find the right stuff.

Last night I drained fluid from the tail end of the trans.  It is the part with a square head fill plug on the right side and a square head drain plug on the lower right side.  I dont know if this is what's called a fluid drive trans or not and that's probably what's leading  all of the confusion for me.  What drained out was like a gear oil consistency but it was very old and needed to be changed.  I'm going to Napa tomorrow to pick up some parts and would like to know what I'm supposed to be putting back in there for fluid.  As well, is there another part of the trans that needs servicing or fluid change or is that the only part?  Thanks in advance.

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thx for responding.  apparently Napa doesn't carry the Gl1 in Canada or at least I cant find it.  Cant find it anywhere else either.  I'm also having great difficulty in finding an equivalent 80w90 mineral oil while searching online.  perhaps when I go to a few stores I may find something.  In the meantime do any Canadian members have any suggestions for an equivalent? or what have you used? thx

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Welcome aboard...........try tractor or similar type places, also truck repair shops........the standard 3 speed trans takes 2 & 3/4 pints of SAE80 Fluid Gear Lubricant, fill to bottom of filler plug hole.........the diff takes 3 & 1/4 pints of Rxtreme pressure Hypoid Gear Oil of SAE 90 for temps above 10 degrees, below 10 degrees use SAE 80 fill to bottom of filler plug hole, do not overfill gearbox or diff......on the diff check that the rear axle air vent is clear and clean of dirt, dust and crap....if obstructed.....clean...........P15 Plymouths had a standard 3 speed transmission using a clutch between the engine flywheel and gearbox..........Fluid Drive was a fluid coupling that took the place of the clutch between the engine and gearbox.........as far as I am aware all 3 speed transmissions should only ever use OIL.........nothing that is called a "fluid" should be used.......not being pedantic just trying to explain that there is a difference and you may get the wrong lubricant if you are not careful...............I would strongly suggest getting a workshop manual and NOT a CD version but an original or reprinted paper copy..........regards from Oz........Andyd     

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now that's about as clear as it could ever get.  thank you for all of that info. I have been left scratching my head with confusion because theres alot of jumbled and conflicting info put there (not talking about this forum).  this clears it up and helps alot.  thx Andyd.

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11 hours ago, woodrow said:

thx for responding.  apparently Napa doesn't carry the Gl1 in Canada or at least I cant find it.  Cant find it anywhere else either.  I'm also having great difficulty in finding an equivalent 80w90 mineral oil while searching online.  perhaps when I go to a few stores I may find something.  In the meantime do any Canadian members have any suggestions for an equivalent? or what have you used? thx

I also was in similar circumstances a number of years ago trying to find a local supplier for plain old gear oil. I spoke with a local business that specializes in rebuilding transmissions  and they suggested using SAE 50 engine oil... I chose not to follow their advice ; as I live close to to the US/Canada border I picked up the gear oil at Napa in Cut Bank MT... Sometime later I came across this oil viscosity chart.

815817312_PlainOldGearOil.jpg.b8617724fc81c48a16eb660d6139914a.jpg1616063258_OilGradeSystems.jpg.15cf9fc5c40c7db225331a02a524c392.jpg

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The gl1 rating I important in that the lubricant formula is free of additives that re not suitable for use where brass, bronze,and other white metals are used in synchronizer parts.  How quickly any negative effect woud be noticed enough to performanceof the transmissions would be at best an educated guess.  With  vintage, limited use vehicle it might be a month or years. Older lubericants are getting harder to find,so if your lube chart specifies them you should probably stock up when you find them. Mother Mopar chose not complicate Pymouth with fancy drive trains till 53/54 when Hydrive was introduced, but these shared egine oil between the engine and trans, no still no exoctic fluids just more good old SAE 30, nine quarts if I recall correctly.

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My local Napa store could not find the GL-1 on their computer either.

I'm in Ca. The very experienced counter man finally pulled out the paper copy of Napa's lubricant book. Still no luck, so I asked if I could look at the book while he waited on someone else.

I found it and the same part # shown in the picture that T120 posted above.

Then I asked the man to punch the part # in his computer that showed they have it available, just not in that store but another about 90 miles away did.  I got the oil the next day!

 

Worth a phone call to your closest Napa store and have them search that 65-201 part #.??

 

DJ

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1 hour ago, greg g said:

The gl1 rating I important in that the lubricant formula is free of additives that re not suitable for use where brass, bronze,and other white metals are used in synchronizer parts.  How quickly any negative effect woud be noticed enough to performanceof the transmissions would be at best an educated guess.  With  vintage, limited use vehicle it might be a month or years. Older lubericants are getting harder to find,so if your lube chart specifies them you should probably stock up when you find them. Mother Mopar chose not complicate Pymouth with fancy drive trains till 53/54 when Hydrive was introduced, but these shared egine oil between the engine and trans, no still no exoctic fluids just more good old SAE 30, nine quarts if I recall correctly.

   My thoughts as well, I bought a case .

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5 hours ago, greg g said:

The gl1 rating I important in that the lubricant formula is free of additives that re not suitable for use where brass, bronze,and other white metals are used in synchronizer parts.  How quickly any negative effect woud be noticed enough to performanceof the transmissions would be at best an educated guess.  With  vintage, limited use vehicle it might be a month or years. Older lubericants are getting harder to find,so if your lube chart specifies them you should probably stock up when you find them. Mother Mopar chose not complicate Pymouth with fancy drive trains till 53/54 when Hydrive was introduced, but these shared egine oil between the engine and trans, no still no exoctic fluids just more good old SAE 30, nine quarts if I recall correctly.

Ive got over a decade of use and 20k miles on my 48 using gl4/5. The bottle did specifically say safe for use in manual transmission. The same bottle no longer says that so ive got to track down some of this older style. 

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8

6 hours ago, Frank Elder said:

Maybe its just me, but I would never drain any old fluid until I had purchased a suitable replacement.....

fact is that I've got the car on jack stands and waiting for a slew of new parts to arrive.  as well, we have another 2 months here before the car hits the road for the season.  the other thing is when I dipped my finger in the fill hole i pulled out a substance that had no business being in there.  just pure neglect and should have been changed years ago.  so it wasnt staying in there no matter if I had a replacement or not.

today I did in fact get the required gear oil.  soon as I mentioned to the guy at the counter at napa what I wanted he knew what the "canadian" equivalent was.  it's in the trans now in fact.

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