Tail Shaft Leak - was "Is this gasket available? A904 Extension Housing Snap Ring Cover"

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DigitalRelay

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Edit: After a closer look, it seems the trans fluid is coming through the tail shaft seal and dripping down. My understanding is that the tail shaft seal is really just a dust cover to keep dirt from going in, not meant to seal fluid. So if that's the case, what would cause this type of leak?

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I've got several transmission fluid leaks on my '74 Plymouth Scamp, /6 auto - and after cleaning things up, it appears one of them is the extension housing snap ring cover gasket. I'm having a heck of a time trying to find a part number or even the correct name for it. Does anyone know if this gasket is available? A part number or source for it would be amazing. Or do I need to make my own gasket for this?

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New pics:

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I don't think there is a gasket the, it's a output shaft seal. The extension housing gasket is between the tailshaft and the case. Both are listed on ROckauto's site and should be available from most any parts store.
 
No gasket there. There is a gasket under the trans mount for the snap ring that is shaped like that.
 
Must be the one next to the extension housing gasket. bottom row, center.

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toolmanmike said:
Must be the one next to the extension housing gasket. bottom row, center.

View attachment 1716304518
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I noticed there were other threads that refer to that gasket as the tail shaft extension housing plate gasket. It sure does look like the one Mike has provided in this photo. That one would be a cake walk to make. The plate would be a perfect stencil.
 
The small one under the plate that gives access to the snap ring for removing the extension housing has many different names online when people talk about it. Should be just a small flat gasket with two holes like the one in this Amazon link below. I thought I found this listed in other places but do not see it right now. Try visiting a local transmission repair shop and see if they can sell one individually. Otherwise, maybe try one of the Mopar specific shops like A&A and transmission, Andrews Racing Transmission, or Cope Racing Transmissions.

https://www.amazon.com/Output-Shaft-Bearing-Gasket-12305J/dp/B0CGSW7XGT?tag=fabo03-20
 
I have never seen an access port back by the seal. That is about where they used to install a big counter weight to keep the back end from dancing. But you can see the mounting points for that , just forward a bit.
The access port for the rear bearing is way further towards the front. up closer to the speed-O housing.

Wait a sec, I just remembered that the very early 904s with the Tri-pot yoke, had a bearing back there somewhere. Hmmmmmmmmmm, IIRC that rear bearing was snap-ringed to the output shaft. So
IDK what you got there.
But what I do know, is that if the Extension-housing was designed for a slip yoke, the RearBushing is right above that strap. Yeah, so; I wanna see what's behind that door; maybe a grease fitting? IDK
Very curious, I am
 
Original post updated, title edited, new pics added in original post. Trans fluid is coming through the tail shaft seal and dripping down. My understanding is that the tail shaft seal is really just a dust cover to keep dirt from going in, not meant to seal fluid. So if that's the case, what would cause this leak?
 
DigitalRelay said:
Original post updated, title edited, new pics added in original post. Trans fluid is coming through the tail shaft seal and dripping down. My understanding is that the tail shaft seal is really just a dust cover to keep dirt from going in, not meant to seal fluid. So if that's the case, what would cause this leak?
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There is a lip seal on the inside that seals against the slip yoke to keep the fluid inside. The outer part is the dust boot.
 
There should be a drain hole in that boot at the bottom to keep from trapping water. Looks like yours might be there but can't tell if it's installed right side up. I poked a hole in mine
 
65TerrorCuda said:
There should be a drain hole in that boot at the bottom to keep from trapping water. Looks like yours might be there but can't tell if it's installed right side up. I poked a hole in mine
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Definitely no holes in mine. It came out pretty easily. The outside rubber is cracking, so I'm guessing the inside wasn't sealing so well. Ordering a new one now.

Thanks again, everyone!
 
DigitalRelay said:
So if that's the case, what would cause this leak?
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Probably either over-filled, or more likely is that the the converter anti-drainback valve quit working, and so, now, when you park the vehicle, the convertor drains back into the trans, raising the fluid level up to the rear seal. Normally, there is very little oil at that rear seal. Normally, with engine running in Neutral, the oil-pan is barely full,
 
The outside boot you see is indeed a rubber dust boot. However, there is a conventional seal made to that that presses into the rear of the transmission tail shaft housing. The rubber boot on the outside seals the outside of the slip yoke from dust and dirt entering into the main seal area and possibly damaging the main seal that seals the yoke and keeps the fluid inside the transmission. Not all those tail shaft seals have the boot, but I prefer them. Kinda gives another layer of protection.
 
AJ/FormS said:
Probably either over-filled, or more likely is that the the converter anti-drainback valve quit working, and so, now, when you park the vehicle, the convertor drains back into the trans, raising the fluid level up to the rear seal. Normally, there is very little oil at that rear seal. Normally, with engine running in Neutral, the oil-pan is barely full,
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How would you fix a converter where the anti drain back valve quit working?
 
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