727 Pump/TQ Hub Seal Leak

JD Erisman

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After having a 727 leak become increasingly large I decided to pull it. I do not see a leak from the vent hole, the perimeter of the pump cover or any cracks. The only place I could see it was leaking was around the TQ hub at the pump seal. The TQ is a Dynamic 9" 3000 above stall, I replaced the seal when I installed it two years ago.

Currently, I bought a new seal, National brand with a flange. I don't know the brand of the old seal. I placed the seal on the Dynamic converter's hub and it is noticeably less snug when compared to my old TCI TQ. The Dynamic converter hub is a couple of hairs smaller in diameter when compared to the TCI but Dynamic told me the difference is negligible. I cannot see what else is the problem and with the difficulty in pulling my tranny I don't want to put the Dynamic back in only to have it leak but I hate not to use it. I thought of sleeving the Dynamic but that might make it too tight of a seal and burn it up. I thought of a smaller ID seal but worry about the same.

Any ideas? Am I over thinking the idea of a smaller ID seal being a problem? Any ideas of how to figure out a smaller seal ID with the other dimensions being the same? I tried the National/Timkin catalog but had no luck deciphering it.

Thanks for any help.
 

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If it is a smaller ID on the snout then it will be loose in the bushing also. Find something to measure the snouts on each and compare.
 

JD Erisman

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The snout on the TCI is 1.87.20. The Dynamic snout is 1.86.90. According to Dynamic that is negligible but the new seal is noticeably less snug.
 

CudaFactHackJob

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Does it leak running or off? A bad pump bushing can leak off but seal running. A Chevy bushing would center that Dynamic converter a lot better, but .030 is a lot. I've seen the same problem on old cruisomatics that folks would install a C4/C6 seal into and have a leak, because the OD of both seals are identical, but the id is smaller on the cruiso. I researched converter repair sleeves but only found front repair kits for the crank/converter. If you could find one, it sounds like a repair kit for a chevy converter would fit better.
 

JD Erisman

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I don’t know if it leaks running or not, I should have checked. It definitely looks as soon as it is parked or stopped and the engine is off. It leaks a lot after it is shut off. I have read of others replacing the bushing with a Chevy but couldn’t find specific years or models (turbo 350 or 400?) and there were warnings of installing them too deep etc.. so I was hesitant to do that.
 

CudaFactHackJob

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Too deep is bs. Just remember to stake it. Maybe Kim will chime in on the specifics of the Chevy bushing. Search on this forum. Did you search for a repair sleeve for the BACK of the converter? I couldn't find one.
 

JD Erisman

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I searched for any associated sleeve and found none, which surprised me. Thanks for all of your help!
 

CudaFactHackJob

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A sleeve that only covers the converter in the seal area would work. But there's probably a seal that would fit tighter.
 

JD Erisman

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A sleeve that only covers the converter in the seal area would work. But there's probably a seal that would fit tighter.
I aske Dynamic, they use a Federal Mogul but didn’t know the part number and I haven’t found that brand of pump seal anywhere. I thought about a sleeve but don’t know how to determine the size I need. They are an extremely tight, pressed fit so I am a little lost as to proper diameter.
 

JD Erisman

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I cannot find an easy to use seal chart fit a part number. All I can find are jumbled catalogs with idles of seals if every type and know way for me to find my existing seal and others to compare size. Or, I’m too stupid to figure out their charts.
 

JD Erisman

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I’m sorry, that last post of mine was full of IPhone “corrections” and reads like a caveman wrote it.
 

transman

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I don’t know if it leaks running or not, I should have checked. It definitely looks as soon as it is parked or stopped and the engine is off. It leaks a lot after it is shut off. I have read of others replacing the bushing with a Chevy but couldn’t find specific years or models (turbo 350 or 400?) and there were warnings of installing them too deep etc.. so I was hesitant to do that.
Maybe I'm late for this, but the 350 and 400 use the same pump bushing as does the aluminum powerglide and the TH180.
 

oldkimmer

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Transman nailed it. The 727 hub is supposed to measure 1.875. U need a factory bushing then. To use the wider Chevy bushing the hub has to measure 1.871 or a little less. And yes the Chevy bushing stabilizes the converter a lot more. Post some pics of the hub. Most importantly measure it. The old saying is that if the seal is leaking the bearing or bushing is worn causing the seal to leak. Replacing the seal only is a band aid fjj in x as u found out. Kim
 

CudaFactHackJob

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Put a Chevy bushing in it and stick the pump half over the converter to check the clearance. If it's too tight; knock it back out and go oem. Don't forget to stake it AFTER the trial fit.
 

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