727 transmission leak

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bbmopars

bbmopars

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I have big block 727 it has a small leak comin from the corner in front towards drivers side.i have change the gasket to a felpro which is made of same material like mopar performance is,any suggestions why?i used black gasket maker sealant when puttin it on.
 
So that would be rubber type gasket?
Stock stamped steel type pan or cast pan?

With the rubber gaskets if you use sealer and over tighten it can push the gasket out causing a leak.

If stamped pan sometimes the bolt holes get dimpled from r&r causing it not to seal.
 
twayne24365 said:
So that would be rubber type gasket?
Stock stamped steel type pan or cast pan?

With the rubber gaskets if you use sealer and over tighten it can push the gasket out causing a leak.

If stamped pan sometimes the bolt holes get dimpled from r&r causing it not to seal.
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Yah its rubber type gasket
 
bbmopars said:
I have big block 727 it has a small leak comin from the corner in front towards drivers side.i have change the gasket to a felpro which is made of same material like mopar performance is,any suggestions why?i used black gasket maker sealant when puttin it on.
Click to expand...
Make sure its not the shaft seal
 
Common places they leak are shift shaft seal, dipstick tube and shaft for rear band lever. If your sure its leaking on the front driver side I would replace the shift shaft seal and go from there. They are almost always bad if they have not been replaced recently. You can do it in the car but its tight. Last one I did on a lift and used a mirror to see what I was doing. Pop out the old seal with a screwdriver and installed with the special tool. You could probably find a suitable deep socket that would work instead of the special tool.
 
MoparMike1974 said:
Common places they leak are shift shaft seal, dipstick tube and shaft for rear band lever. If your sure its leaking on the front driver side I would replace the shift shaft seal and go from there. They are almost always bad if they have not been replaced recently. You can do it in the car but its tight. Last one I did on a lift and used a mirror to see what I was doing. Pop out the old seal with a screwdriver and installed with the special tool. You could probably find a suitable deep socket that would work instead of the special tool.
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yep from the front corner on transmission pan it is the only leak
 
I agree with Kidwell. You have to look very closely. That seal for the manual selector shaft will run forward, causing you to think it's the pan.
 
Here's a selector shaft tool, took me 15 mins to replace one.

Seal removal tool.jpg
 
Where is that on a big block 727 the shaft seal selector?
 
bbmopars said:
yep from the front corner on transmission pan it is the only leak
Click to expand...

The front band adjuster and cooler output line are both right there in that corner also.
If you are absolutely sure it's coming from the pan take it back off and tap that corner up a little.
Also make sure your bolt holes are flat, or even just a little bit dimpled down.

Sometimes you can even get away with tapping the pan rail up while the pan is still on and stop a leak.
 
Follow the linkage down to the trans. Throttle pressure and shift linkage attach at same place. A shaft inside another shaft, sticks up through a seal.
 
TrailBeast said:
The front band adjuster and cooler output line are both right there in that corner also.
If you are absolutely sure it's coming from the pan take it back off and tap that corner up a little.
Also make sure your bolt holes are flat, or even just a little bit dimpled down.

Sometimes you can even get away with tapping the pan rail up while the pan is still on and stop a leak.
Click to expand...
tap with a regular hammer? You wouldn't have to unloosen any pan bolts when tapping?
 
Only two choices: either learn how to straighten a pan and knock down the holes slightly below level (as was already suggested) and use a cheap red fiber gasket; or buy an aluminum pan so it will seal with any old kind of cheapo gasket. Just don't use a cork or rubber gasket with the stock pan.
 
Tap the corner of the pan little it did help slow it down alot.i ended gettin some of spray n seal leak repair made by pertmex. It finished sealin the leak up.
 
Mine was leaking also, I first thought it was the pan. Bought a new stamped pan sealed up really good, still leaked but turned out to be the shift shaft seal. With the 2 1/2 in TTI pipes and bad fingers ( arthritis ) I couldn't get in there to change it so I took it to a buddies transmission shop and had him change it. Best $50.00 I ever spent. But I still have a leak and it seeping from the front coolant line . I have replaced the brass fitting a couple of times and replaced the line it's self but still can't get it to stop seeping. Last time I changed the fitting I used Loctite sealant 567 on the threads and she still seeping. I was thinking about trying Ultra Black gasket sealer next. Unless someone has a better way to seal it might have to take it back to the tranny shop.
 
68 Coronet RT said:
Mine was leaking also, I first thought it was the pan. Bought a new stamped pan sealed up really good, still leaked but turned out to be the shift shaft seal. With the 2 1/2 in TTI pipes and bad fingers ( arthritis ) I couldn't get in there to change it so I took it to a buddies transmission shop and had him change it. Best $50.00 I ever spent. But I still have a leak and it seeping from the front coolant line . I have replaced the brass fitting a couple of times and replaced the line it's self but still can't get it to stop seeping. Last time I changed the fitting I used Loctite sealant 567 on the threads and she still seeping. I was thinking about trying Ultra Black gasket sealer next. Unless someone has a better way to seal it might have to take it back to the tranny shop.
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that would work or this stuff i used.
https://www.permatex.com/products/adhesives-sealants/permatex-spray-sealant-leak-repair/
 
This stuff dosent work,fluid eats this stuff right up.makin it a really gummy and not sealin.they make a pertmex rtv that is strictly made for automatic transmission fluid.
 
bbmopars said:
Tap the corner of the pan little it did help slow it down alot.i ended gettin some of spray n seal leak repair made by pertmex. It finished sealin the leak up.
Click to expand...

That stuff actually works ?? How well did u clean the area before hand ?
 
famous bob said:
That stuff actually works ?? How well did u clean the area before hand ?
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i clean well it well with brake cleaner the area,transmission would eat right through.it help slow down the leak alot. i decided to pull the pan,fix it right.i don't need to waist fresh fluid from it leakin.flex seal is a stronger seal and will stop the leak for awhile its a temporary fix.
 
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