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Who knows about shaft seals?


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I am rebuilding an oilhead transmission that had leaking input and output shaft seals. The transmission spent some time in storage and there was a bit of rust & crunge under the shaft seals and I assume that this is why they started to leak (at relatively low mileage.)


I've cleaned up the shafts in the seal area (using some 400, then 1200 wet sandpaper, then polishing with a Dremel) and now they are perfectly smooth in both appearance and touch, except for a very slight amount of very tiny pitting in a few areas (barely visible to the naked eye, almost requires a loupe to see it.) My questions is... is this good enough to return to service? I don't want to take any significant amount of metal off (which I think would have a higher likelihood of doing harm than good) and I would think that perfectly smooth to the touch would be good enough to ensure long seal life. Would appreciate any comments from anyone who has a lot of experience in this area...

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Seth, that is a tough call.. The company I work for runs thousands some years even millions of miles of automotive durability testing a year & seal leakage was/is/has been a constant problem for years.. I have seen seals run on the nastiest rusty shafts with not even a hint of seepage & other times the shafts looked like glass with no shaft run-out or axial play & they would seep like an old mahogany boat..


Your shafts sound reasonable & as long as the shaft diameter is within specs in my experience a seal should hold.. As long as the seal gets a reasonable amount of lubrication the slight surface imperfections shouldn’t be a big cause for concern.. High RPM’s with poor shaft lubrication & a seal won’t gold up for long on a non perfect shaft though..


Are these single lip seals? If so any chance in finding same spec double lip seals?


Is the shaft seal surface the same or larger diameter than the shaft ends? If so you always have speedy sleeves.. I have had good luck with those on old seal grooved or pitted shafts.. As long as you can get them on the shaft they work great..


Keep in mind this isn’t my area of expertise so the above is more from experience not education..



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I hadn't heard of Speedi-Sleeves Bill, thanks for that tip. I don't think my situation is nearly bad enough to require something like this but I'll definitely keep the product in mind should I turn out to be wrong. For anyone else not familiar with Speedi-Sleeves here is some info.


I'll try to look around and see if a double-lip seal is available for this application (I need one each 22x35x6, 25x40x6, and 20x35x5.) You also have me thinking... since in this case there seems to be enough room to do so couldn't I just install two (single-lip) seals in tandem?

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~~~... since in this case there seems to be enough room to do so couldn't I just install two (single-lip) seals in tandem?

Seth, I have done that on older farm equipment & older low RPM hydraulic pumps with real good success.. Never tried in on high speed shafts but can’t see any reason it won’t work..


Be sure to pack grease between the 2 seals as the outer seal lip won’t receive any primary lubrication from the gear oil..



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