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reluctantartist Samba Member
Joined: August 13, 2006 Posts: 1927 Location: Bloomington, IN
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Posted: Fri Jul 18, 2014 6:52 am Post subject: Pesky transmission pan leak |
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I have a persistent leak on the transmission pan. I have gone over it to make sure it is flat. I used a rubber gasket. I put a very thin coat of rtv between pan and gasket and it still leaks. My next step is to use a thicker coat of rtv between the gasket and pan. Does anyone have any other suggestions? And when I use the rtv I put on then the gasket and let it sit overnight under a piece of plate glass with weight on it. _________________ 1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them. |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21474 Location: Oklahoma City
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Posted: Fri Jul 18, 2014 10:13 am Post subject: |
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Wait.....there are a few methods that work well you should consider. Typically the rubber gasket does not work as well with the automatic transmission pan. Its not stiff enough.....but can work well if you do a couple of things.
Do not put wet RTV on the gasket/pan assembly and tighten the bolts regardless of whether you use the stock rubberized cork, flat gasket paper or rubber (all have been available for this transmission).
This will virtually guarantee a leak because the wet RTV allows the gasket to squirm.
The two most effective methods I have found...and I have done many 003 pan gaskets....are as follows.
Note: neither of these are fast jobs. You cannot make a sealed pan in less than an overnight wait. And...the thinner the RTV...the better the seal and holding power.
1. If the pan is less than perfect....meaning fairly normal...has had a few distortions but you have straightened it well.....clean the pan surface and the machined gasket area of the transmission well and wipe with a fast flashing clean solvent like acetone. Do this to both sides of the gasket as well.
You need to first drain the transmission, and spray something fast evaporating like carb cleaner around the sealing area and then repeatedly wipe over a period of an hour or so. You must make sure there are no drips of ATF that will get onto the sealing area.
The sealing areas must be oil and grease free.
Lay the gasket and pan on paper towels. Put on your nitrile gloves. You need to use Permatex Ultra copper...or equivalent....but the copper is the best and their most oil proof.
You will put a layer of it on the pan first then the pan side of the gasket.
DO NOT SQUEEZE OUT AND APPLY A BEAD OF RTV.
You want the RTV no thicker than about .002'.005" at most. If you spread it on then stipple/dapple it rapidly with your fingertip....it creates an even uniformly textured surface of uniform thickness. The faster you move your finer up and down the thinner it will be. The slower you move...the thicker and deeper the texture. Do this to both the gasket and the pan.
Place the gasket on the pan DO NOT SQUEEZE THEM TOGETHER.
Now...repeat the application on the top side of the gasket and the sealing area of the transmission case.
Make sure the holes are lined up. No apply the pan to the transmission...put a bolt in on each corner to keep it level and put all bolts in. Screw them in just LIGHT finger tight...so perfect contact is made....and some RTV just starts to squeeze from the edges. With this method there is not much RTV...so you have to look close. Make sure all the bolts are equally screwed in.....but only light finger tight.
Stop now...and let the RTV cure overnight...no kidding...or at minimum 6-8 hours.
Make sure all the bolts have good lock washers...schnoor lock washers are better but split will do.
There is no actual torque value that works properly for this.
In the morning using a /4" ratchet and socket bit with the palm of your hand on the ratchet head....tighten each bolt up...just until you feel resistance....then move diagonally to another. When they all feel even tension...only tighten 1/4 turn more....work all the way around. If some feel loose...give no more than a 1/4 turn. Maybe two trips around like this. You are probably looking for about 3-4 ft lbs max.
The object is to let the RTV set up so it cannot squeeze out and let the gasket squirm.
2. The second method is identical but works best for perfect transmission sealing surface and pan that has no scratches, dents or high and low spots. You will need a sheet of glass or plexiglass and a hard rubber roller (called a brayer) from Hobby lobby or similar.
You squeeze the RTV out on the glass and roll it rapidly with the roller. It shears the RTV to one uniform thickness based upon the shear ability of the RTV and the temperature . Usually that thickness will be (based on repeated testing with my wet film thickness gauge) about 15-20+ microns...just under .001"...and will be very uniform. The thickness of RTV on the roller will be uniform as well and slightly thicker.
Then roll this onto the pan and gasket...refilling the roller on the plate glass as needed. It makes a perfect deposit thickness for the very best seal.
Then apply gasket to pan...pan to tranny...finger tight again...wait for cure...final tighten.
Ray |
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Tram Samba Socialist
Joined: May 02, 2003 Posts: 22697 Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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Posted: Fri Jul 18, 2014 12:18 pm Post subject: |
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The other thing that helps is to rough up the sealing surfaces of the pan and the trans with some 320 grit sandpaper to give the sealant a surface to "grip". I've found that black or clear Permatex silicone adhesive sealant- not just silicone or RTV- gives a bulletproof seal _________________ Немає виправдання для війни! Я з Україною.
Bryan67 wrote: |
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ubercrap Samba Moderator
Joined: July 01, 2004 Posts: 1060 Location: Ridley Park, PA
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Posted: Tue Jul 22, 2014 9:49 am Post subject: |
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Tram wrote: |
The other thing that helps is to rough up the sealing surfaces of the pan and the trans with some 320 grit sandpaper to give the sealant a surface to "grip". I've found that black or clear Permatex silicone adhesive sealant- not just silicone or RTV- gives a bulletproof seal |
. So this stuff is OK to use with the transaxle temps? I believe it specifically says not to use for engine gaskets, but could imagine lower temps in this application? What about fluid resistance? Not sure I want to go through contortions of Ray's methods (no offense, I'm sure they work great!)to seal mine that leaks as well since I don't have unlimited time. _________________ '74 412 wagon
(2) '74 412 2dr. sedan
'73 412 2dr. sedan |
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Tram Samba Socialist
Joined: May 02, 2003 Posts: 22697 Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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Posted: Tue Jul 22, 2014 11:05 am Post subject: |
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ubercrap wrote: |
Tram wrote: |
The other thing that helps is to rough up the sealing surfaces of the pan and the trans with some 320 grit sandpaper to give the sealant a surface to "grip". I've found that black or clear Permatex silicone adhesive sealant- not just silicone or RTV- gives a bulletproof seal |
. So this stuff is OK to use with the transaxle temps? I believe it specifically says not to use for engine gaskets, but could imagine lower temps in this application? What about fluid resistance? Not sure I want to go through contortions of Ray's methods (no offense, I'm sure they work great!)to seal mine that leaks as well since I don't have unlimited time. |
I've never had any issues using it with a gasket. I used to use this stuff to put oil pan engine heaters on oil pans in my Sun Valley Idaho shop. The temps never bothered it. One time, a customer's daughter ran her Audi 5000 out of coolant and badly overheated the engine, necessitating replacement. When I went to transfer the heater, I couldn't.
It's tough stuff! _________________ Немає виправдання для війни! Я з Україною.
Bryan67 wrote: |
Just my hands. And a little lube. No tools. |
To best contact me, please use the EMAIL function in my profile |
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reluctantartist Samba Member
Joined: August 13, 2006 Posts: 1927 Location: Bloomington, IN
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Posted: Sat Sep 20, 2014 8:11 am Post subject: |
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Okay I am dealing with this today and was wondering about using indian head shellac instead of the copper rtv i have. Any one welse with experience with this? Is this a bad idea? _________________ 1982 Westy, 1974 412 Variant... Yes, Aircooled's are great! Oh and I do have modern computer controlled vehicles too, but I just don't care about them. |
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Tram Samba Socialist
Joined: May 02, 2003 Posts: 22697 Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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Posted: Sat Sep 20, 2014 11:35 am Post subject: |
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reluctantartist wrote: |
Okay I am dealing with this today and was wondering about using indian head shellac instead of the copper rtv i have. Any one welse with experience with this? Is this a bad idea? |
Again, use the Permatex Adhesive Sealant with a gasket and let it set up overnight- you'll never have an issue. _________________ Немає виправдання для війни! Я з Україною.
Bryan67 wrote: |
Just my hands. And a little lube. No tools. |
To best contact me, please use the EMAIL function in my profile |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21474 Location: Oklahoma City
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Posted: Sat Sep 20, 2014 3:40 pm Post subject: |
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Yes.....what he said. You can also uss virtually any high temp oily location RTV like permatex ultra to adhere the gasket to the PAN SIDE ONLY. Let it set up over night. Do not apply any product wet. The gasket will squirm.
I love Indian Head.....but this is the wrong place for it. You will never get it off the pan. Ray |
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