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Jul 21st, 2025 | | | | Joined: Nov 2011 Posts: 1,608 'Bolter | | 'Bolter Joined: Nov 2011 Posts: 1,608 | Hey all,
Tearing into an old Chelsea PTO and need some guidance. The gear shift shaft seal is toast and I am searching for a replacement. Unfortunately the oddball shaft diameter of 0.621 is coming up with no modern equivalents. There are several options if I use a seal that is made for a 0.625 shaft. Will a seal that is designed for a shaft 0.004 larger work?
Paul | | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | If the seal has a "garter spring" holding the seal lip to the shaft, it should work. Is there any pressure on the seal, or is it just there to prevent lube from migrating out of an atmospheric-pressure reservoir?
The closest metric equivalent would be a 15.5 MM at 0.614".
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Nov 2011 Posts: 1,608 'Bolter | | 'Bolter Joined: Nov 2011 Posts: 1,608 | Jerry,
The seal will only see slight lateral force when shifting the PTO gear in and out, but the seal is below the transmission fill plug so it will be constantly immersed in 90 weight gear oil. The "close" 0.625 inch seal does have the garter spring. The application is a 1942 non-syncro 4-speed under atmospheric pressure.
From your advice it sounds like the garter spring can "absorb" a certain range of shaft diameter? Any ball park rule of thumb on this kind of stuff?
Thanks, you have been a big help.
Paul
Last edited by Paul_WNC; 11/22/2015 2:25 AM.
| | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | Unless the shaft is worn undersize and/or the bushing it runs in is sloppy, I doubt if .004" is going to present a problem. Check for any up/down/sideways motion of the shaft in the case, which is what usually causes sliding shaft seals to seep leak.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Nov 2011 Posts: 1,608 'Bolter | | 'Bolter Joined: Nov 2011 Posts: 1,608 | The shaft does not have any measurable wear and neither do the bushings. I will let you know if see leaks when I get this all together. Thank you for the guidance.
Paul | | | | | Joined: Feb 2013 Posts: 56 'Bolter | | 'Bolter Joined: Feb 2013 Posts: 56 | Jerry, is there a speedy sleeve small enough to take up the clearance? I cannot remember if they go that small or not.Pat
1966 Chevy C 30 1 ton truck
| | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | The repair sleeve would have to be an inch or more long, since the part in question is a sliding shift linkage shaft, not a rotating one. I don't think the slight undersize will matter, particularly since the seal will not have any pressure applied to the lip.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
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