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Discussion Starter #1
OK, so I've had this problem before and solved it a couple times, but this time no luck, my pan is leaking, and leaking a lot, tried three times and all different methods and it just leaks a ton, not small drips.

Here's the deal, there are absolutely no leaks at the dip stick tube, shifter seal, or any of the band adjustment nuts, it's absolutely my pan. Also, I have done the powder test to see if it's between the gasket and the pan or between the gasket and the case. Unfortunately it's between the gasket and case, the pan is not showing seeping between it and the gasket and the pan is dead straight, no waves (by the way, it's an OEM steel pan and I don't want to use an aluminum pan, it's a concourse car)

So now that I've confirmed it's between the case and gasket what do I do? I've tried every type of gasket.

I just rebuilt my tranny and I'm kicking myself for not getting the case machined while it was out and down to just the case, stupid :(

If a silicone or RTV is my only hope, can you please specify what brand use with Type F tranny fluid and method for applying it? I've never had to use anything previously on a transmission pan so this is super frustrating and wouldn't even know where to begin.

Thanks in advance for any suggestions.

Jason
 

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I've never had an auto trans pan leak that couldn't be solved with a proper straightening of the pan rails (or a new pan in extreme cases) and a Farpak gasket. I've never had to use sealant of any sort and never recommend it. That said, Permatex now makes a sealant that is says is specifically designed for use with ATF and it's available at Amazon, Advance etc.

https://www.permatex.com/products/gasketing/gasket-makers/permatex-automatic-transmission-rtv-gasket-maker/

If it were me, I'd drop the pan and clean the case religiously. Then, use a large flat file and dress the case and rail surfaces. Often you'll find a burr or nick in the surface this way and can work it out flush with the surrounding surface. Keep at it until the whole rail looks the same, then clean it with brake cleaner. At his point, I'd also inspect it for a crack. It should be fairly easy to spot with the dressed surface.

I'd then try the Farpak gasket with no sealer. If the rails and case are true, it will seal. If it still won't seal, then I'd lay a 1/16" ~ 1/8" bead along the gasket, going around each bolt hole. Do both sides and let it set up for ten minutes or so, then install.
 

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Discussion Starter #3 (Edited)
I've never had an auto trans pan leak that couldn't be solved with a proper straightening of the pan rails (or a new pan in extreme cases) and a Farpak gasket. I've never had to use sealant of any sort and never recommend it. That said, Permatex now makes a sealant that is says is specifically designed for use with ATF and it's available at Amazon, Advance etc.

https://www.permatex.com/products/gasketing/gasket-makers/permatex-automatic-transmission-rtv-gasket-maker/

If it were me, I'd drop the pan and clean the case religiously. Then, use a large flat file and dress the case and rail surfaces. Often you'll find a burr or nick in the surface this way and can work it out flush with the surrounding surface. Keep at it until the whole rail looks the same, then clean it with brake cleaner. At his point, I'd also inspect it for a crack. It should be fairly easy to spot with the dressed surface.

I'd then try the Farpak gasket with no sealer. If the rails and case are true, it will seal. If it still won't seal, then I'd lay a 1/16" ~ 1/8" bead along the gasket, going around each bolt hole. Do both sides and let it set up for ten minutes or so, then install.
Thanks for the response, the pan is dead straight and I've tried all the different gaskets including Farpak. I clean both the surfaces extremely well with brake cleaner before installing the pan and gasket, torque to 65 inch pounds in a criss cross manner, let sit for a couple hours, then torque to 90 inch pounds let sit for 24 hours, then torque to 105 inch pounds then sit for 24 hours, check torque one last time then fill. Check it and it's definitely leaking between the case and gasket, not the pan and gasket.

So with that said now, if I do the flat file you suggest (which was what I was thinking was next) what coarseness file would you use.

I obviously DO NOT want to use any RTV, only as a very last resort and marked as a fail ;)

Also, here's a picture of how much fluid is leaking just after 12 hours, it's a lot.

Thanks,

Jason
 

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That's a lot of fluid in 12hrs! Really beginning to wonder if your case is cracked.

The file I use to dress surfaces is a dual American pattern 8", single cut on one side, double on the other. Single cut leaves a smoother finish, double cut removes material quicker. For aluminum I prefer the single cut unless I'm really impatient... ;)
 

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Pull your pan(again) and run a good straight edge along the bottom of the case and see what you can see.


If you are having your car judged, will they look to see a cork gasket down in there? If not, switch to one of the non-cork gaskets. I glue mine on with aviation permatex which is a mess to clean off later but it definitely sticks the gasket. Coating around the bolt holes is a must because this is a place where they are prone to leak.



So anyway permatex makes this stuff specifically for transmissions;


https://www.permatex.com/products/gasketing/gasket-makers/permatex-automatic-transmission-rtv-gasket-maker/
 

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I thought I had a leaky pan after 4 different attempts, the size of the puddle was the equivalent diameter of an apple after 24 hours.
I used cork and rubber gaskets.
Flattened the pan.
In the end i used the grey oil resistant RTV from Permatex in a tube.
I even checked the dipstick.
Sealed both top and bottom of new gasket and still leaked.

It turned out that after all my efforts my issue was a leak from between the bellhousing and the main body, I believe it is an O ring on the input shaft. Very hard to find as it dribbles down the front case and onto the pan.
I found it by dusting baby powder over the trans.

Keep looking and would highly recommend the baby powder treatment.

After all of that I hated the C4 that much, I swapped it out for a toploader.
 

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Discussion Starter #7
Thanks guys for all the suggestions. Did the powder test previously and can report no visible signs of a crack, just literally seepage between the gasket and the case, no other areas are leaking. I think it's literally the beat up case edge so going to give it a flat file and see what happens. Really can't believe I didn't get it machined while I was rebuilding it, feel so stupid now :)

I'll report back after I attempt the file method and see if that does the trick.

Thanks,

Jason
 

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I know this isn't right but I also used valve cover load spreaders which I feel spreads out the torque the bolts puts down on more then one spot on the pan. I used something like this:

https://www.autozone.com/external-engine/valve-cover-load-spreader/spectre-performance-valve-cover-load-spreader/309803_92057_12420

I figure since the Oil pan in my old 89 Mustang has a factory metal piece that does the same this should help. This is what my 89 had:

https://lmr.com/item/M6674302/frpp-oil-pan-reinforcement-rails-7995-m-6674-302?utm_source=google-shopping&utm_medium=comparison-shopping&utm_campaign=google-shopping-v2&year=1979&adpos=1o6&scid=scplpM6674302#1979&sc_intid=M6674302#1979&gclid=EAIaIQobChMI96vSptS23gIVxoSzCh3VqAThEAQYBiABEgJuyvD_BwE

Actually surprised no one has made something similar for C4 pans, but I guess you just replace your C4 pan with a heavier duty steel/cast metal one.
 

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I'd like to see this one in person, sounds like it's resisted a lot of effort.

I use a 12" single cut mill file. On the case edge and the pan. But really I'm suspecting a crack or gouge in the case sealing surface if you are losing that much. I really really prefer "paper" gaskets over cork but if there's a gouge cork has a better chance of filling it.


"The Right Stuff" is likely the best weapon of last resort and very good stuff. But really most of the time if I need to use RTV to seal something related to a transmission I use Permatex's Ultra Gray. It's good quality stuff and the gray color makes it next to invisible next to cast aluminum. The only worse thing than having to resort to RTV is to have it leaving nasty bright orange or red boogers to let everyone know what you did.
Now Chrysler has long been sealing some of their pans at the factory with what suspiciously resembles The Right Stuff. it works well for them because the parts involved are sanitary clean and PERFECTLY dry. The best RTV you can get won't stick to oil. ATF is oil and if you've had a pan or two off you know it will drip for hours and there's always that one spot dribbling onto your sealing surface. Which is why I use gaskets. Mostly.

So if you can get both sealing surfaces perfectly free of oil long enough to apply RTV. The pan is easy to clean and dry. Lay a bead all the way around and then flatten it with your finger. You want it spread all over the sealing surface and about 1/8 inch thick but this isn't a really precision operation. Enough to make the seal but not so much it gorps out everywhere. Now if you are racing drips you want to be quick. Put RTV on your finger and quickly "paint" the transmission surface. Very thin even coat. All you want is it to stick well to the case. As little as possible down in the bolts holes but speed is essential. Now plop the pan on and get bolts in. DO NOT let the RTV "skin over". The idea is to glue the two surfaces together. letting it skin just tosses the entire concept out the window.

This is kind of a pain in the butt and only a weapon of last resort. And I agree, a "fail". But if you do it correctly without any ATF interfering with the process you can about guarantee your case has a crack you should be able to find with powder even if you couldn't before.

Don't use sealer/RTV in combination with a gasket. That never really works and makes a silly mess to clean up next time. Permatex's "transmission" RTV is just slightly thicker RTV and gets a resounding "meh" from me.
 

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I've used Aviation-Form-A-Gasket with good success on the cork gasket. When you take the cap off there's a brush inside attached to it. I've built many a VW air-cooled motor and used it on cylinder bases and push rod tube end seals. They never leaked. I like it better than the thick RTV which can squeeze into the trans pan if used too liberally and gum things up.
 

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Just a FYI... '64 and a half through '66 cars use these Tranny Gaskets pictured below. They are the correct ones...If you Notice, There are NO Notches. These are the CORRECT Factory Ford C4 Gaskets for '64.5 , '65 and '66. Most people use the wrong gaskets for the Early C4's which causes leaks. You can buy them made in Rubber Gasket Material as well other than Cork. People sell them on Ebay. If you have a '64.5, '65 or '66 Early "Green-Dot" Transmission and you are not using this EXACT shaped Gasket below....then you are using the WRONG C4 Tranny Pan Gasket. The one below is the one that you should be using.


1964 through 1966 C4 Tranny Gasket:
 

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What Mark said -Lube Locker - it works had a similar problem - also look at Hylomar gasket compound not cheap $30 for 3.5oz but also works on anything....good luck!
 

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Hard to believe it is the pan dropping that much fluid over 12 hours. When you have replaced the gasket, have you tried just putting in 3-4 quarts and then NOT starting the car? Then, if it does not leak over the course of 24 hours, you can eliminate the pan, case and gasket as the problem.
 

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Discussion Starter #18
Ok, so pretty much everything that’s been mentioned I’ve tried through the course of getting this thing sealed up, lubelocker gaskets, the correct no cutout cork gaskets, and all the other gaskets recommended. You have to realized I’ve dropped this pan about six or seven times just on this rebuild and previously before the rebuild so many times, it’s been an ongoing issue with this trans. Believe me I’ve read over a 100 posts and recommendations and researched up and down. I’ve done the powered checks and searched high and low for other areas where it’s leaking from. It’s definitely between the case and gasket.

I dropped the pan again last night and cleaned the hell out of it, there are no cracks but some pretty bad deep gouges. I really, really do not want to use RTV unless it’s a last resort which is why I asked about recommendations.

After all this and much consideration last night I’ve decide to pull the tranny again and take it back down to the case again and take it to my machine shop and have them plain the case edge down. It’s my own fault and I should have done it when I had it down to the case a couple months ago.

The good news is I’ve done this before so it should go quicker and easier this time.

Anyway, thank you everyone for all the suggestions and chiming in on this annoying issue, but I feel like if I do this I will not have this issue in the future and it’s probably in the long run the best choice. The transmission performs really well when driving and it being the special correct original HiPo C4 for my K-Code, replacing it is not an option for me 😉

I’ll report back after it’s completed.

Thanks again,

Jason
 

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You really took a higher road than I expected. I'm sure a flycut off the edge is the correct way to go. While you have it there ask if they can check the case for cracks. Just because. Actually you or anybody can because it's just a matter of investing in a two spray can dye check kit from someone like Magnaflux. You don't need the equipment for checking like you do for cast iron, just the spray dyes.

If you haven't already, run the case through a glass bead or walnut shell blasting. It makes the case look beautiful and brand new.

For you folks with time and more than a small amount of patience you can accomplish the same thing with something called "hand scraping". Usually done on iron and steel, the same technique works on aluminum. And is a heck of lot easier because the subject material is so much softer. Properly done you can "flatten" a surface to be more correct than any machine your local machine has in their arsenal. People have been using hand scraping for well over a hundred years on stuff like lathe beds where it's absolutely critical they be flat and straight. Google if you're interested.

I mention this because I have the ability to flycut things and can imagine a shop being a bit less than enthusiastic about mounting a transmission case in one of their machines. It's doable, just a bit out of the ordinary.
 
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