Leaking 727B transmission (2024)

What am I looking at, and how do I stop it from weaping? Pics are looking at rear of transmission. Also installed cork gasket, checked pan for straight clean gasket surface, torqued fasteners according to service manual and still have leak at gasket. Any other suggestions?

Looks like a peanut butter and jelly sandwich. I know you said torqued to proper spec, but it really looks like that cork gasket is ripping right out of there in the pic you sent. Maybe El-Cheapo cork??? The Moroso Blue reusable gasket has been awesome for me......you know us racers feel defeated if we leak one drop of anything out of our vehicles..... 69SleeperBee is right, if the O-ring from the rear band strut is leaking down, or any other source from above, then the pan will take the blame before dripping off. Maybe blast clean with some brake cleaner and give it a look while running to see what shows up??

**EDIT** Since the trans case is aluminum, I normally use some Blue Loc-Tite on the bolts, and like others have said, barely torque them to the required amount...once you have a base built up on the threads with the Blue, you can always go back and give them a little more snug if the need arises.

dvw said:

The Band shaft can be sealed from the outside. Clean the area with brake clean. Blow it dry. Apply a small amount of RTV over the band pin. Cork gaskets work fine. Pan must be straight, no sealer, do not over tighten. By your picture, yours is definately over tightened. Use a nut driver. No need for a ratchet. Then go around a few times. It will settle. Watch the gasket. When it just starts to buldge it's plenty tight.
Doug

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The RTV idea sounds interesting. Is that a quick fix in a pinch? Does it hold up well exposed outside the case?

69 Sleeper Bee said:

That’s the new gasket ?
Looks like your 0 ring is leaking

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It was new a year ago. I now see the repair manual torque is too much. Pinched so much that cork corners are breaking away. But the undercarriage is well oiled. Don’t need the undercoating.

1963JAM said:

The RTV idea sounds interesting. Is that a quick fix in a pinch? Does it hold up well exposed outside the case?

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If it's clean it's a permanent repair. I like Ultra Grey RTV. I add it to the pin on every torqueflite I build. A 727 doesn't have to leak. I've built 30 or more in the last few years. No leaks.
Doug

Dave6T4 said:

I like the factory "o" ringed pan gasket used in the A518 truck transmission. They are reusable, but require longer pan bolts to do the job right.

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What is the torque on the o ringed pan gasket so Hercules doesn’t crush another gasket?

Stick a piece of aquarium hose down the dip stick tube and syphon the transmission fluid out. Lift the *** end of the car to be certain there's no fluid that can weep around the pivot pin. Clean everything, scrub, clean, scrub, clean, scrub clean and seal up the rear servo band pin and I bet your "leaking pan" goes away. I used PRC for aviation fuel tanks. Hasn't leaked a drop...

Are you also certain that your shifter and throttle shaft seals aren't leaking.....

I have 3 automatics in the shop. None of them mark their territory anymore!!

dadsbee said:

Stick a piece of aquarium hose down the dip stick tube and syphon the transmission fluid out. Lift the *** end of the car to be certain there's no fluid that can weep around the pivot pin. Clean everything, scrub, clean, scrub, clean, scrub clean and seal up the rear servo band pin and I bet your "leaking pan" goes away. I used PRC for aviation fuel tanks. Hasn't leaked a drop...

Are you also certain that your shifter and throttle shaft seals aren't leaking.....

I have 3 automatics in the shop. None of them mark their territory anymore!!
View attachment 1405072

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I’m dropping the pan to replace the crushed cork gasket. I that PRC permanent? What did you use for the pan gasket?

1963JAM said:

I’m dropping the pan to replace the crushed cork gasket. I that PRC permanent? What did you use for the pan gasket?

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Plain old cork vs fancy smansy. No sealer against the case side and a little line of aviation gasket sealer around the outer edge pan side.

The PRC on the rear pivot pin is on there good, but can be mechanically removed. You don't want to pay for it though at $200 a pint. I just happen to have stock of it. As DVW noted Ultra Gray RTV will work just fine, just make sure you let it cure before refilling.

zyzzyx said:

The O-Ring can be purchased at an auto parts store or hardware store. Just make sure it's Nitrile.

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Where's the O ring? Does the shaft have to come out of the case? Looking through 66 service manual and don't see what I'm looking for.

dadsbee said:

The o ring is ON the pivot pin. You have to remove it to change it.. or them. Some have two.

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To remove the pivot pin, looks like the tail shaft housing has to come off?