904 transmission pan gasket

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Dennis Gerard

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904 transmission pan gasket leaking anything I should know before pulling pan off and replacing gasket?
 
904 transmission pan gasket leaking anything I should know before pulling pan off and replacing gasket?

Get the rubber over metal gasket from the dealer for a 42RH or 42RE trans.
They seal really well and are reusable.
I know it's kind of a pain in the butt, but there is also a small metal plate that covers the output shaft bearing snap ring that is normally cork and leaks just under the trans mount.
These can look like a pan leak since it is so close to the pan.
(Just so you know it's there)
 
Selector shaft seal, 'O' ring at dipstick tube, etc... can look like pan gasket leak too. Good luck
 
Dipstick tube on passengers side, Selector shaft, speedo input, and more on drivers side. My point is so many places above the pan can leak. The fluid runs down wicks along the pan gasket and pan. Of course the leak can be the pan gasket but it will pay to closely inspect for a higher source of the leak.
 
Don't use rubber or cork. There's a reddish fiber l like. Lay the pan rail on a hard ledge and tap down the holes until they're slightly below the gasket surface. I tighten the bolts tight with a quarter inch drive. Sealing stock pans with a cheap.gasket is an art that l have mastered.
 
It's no big secret that I'm a big fan of the Permatex called The Right Stuff - black.
I use it liberally on both sides of the gasket and basically the gaskets is there for something that will rip apart when the time comes. I did this on my son's Power Wagon a year ago drove it to Colorado and I could almost guarantee you could go there turn it upside down and eat a white bread sandwich off of it. But as mentioned there's so many other places it could leak I would be looking and spraying Parts cleaner up there cleaning it all and wiping it all and then re-running it and make sure it's not coming from the selector or one of the other places like the speedo cable or something.
 
I don't use sealer. I use carb cleaner on the mating surfaces. After a year l can remove all the bolts and sometimes l have to pry the pan off. Just good clean surfaces and a gasket that won't squish and split under pressure like rubber and the cork ones will. I use up extra cork and rubber ones on aluminum pans.
 
If you pull the pan adjust the rear band even if the trans seems to be working right. I've seen several occasions of the rear band needing adjusted and you have to drop the pan to do it.

BTW: I like the re-usable gasket like TB mentioned. Sealer works but is messy. The re-usable needs no sealer and if need be you can reuse it several times
 
Dipstick tube on passengers side, Selector shaft, speedo input, and more on drivers side. My point is so many places above the pan can leak. The fluid runs down wicks along the pan gasket and pan. Of course the leak can be the pan gasket but it will pay to closely inspect for a higher source of the leak.

Agreed.
I used to be in the trans business so I am pretty good at determining specifically where leaks are coming from.
Yet still it's really hard to tell for sure sometimes.
If it's questionable I like to wipe the area down and spray a little aluminum bomb on the area and go back to check it after a drive. (dont paint it, just a light barely noticable coat)
the fluid leaves a real definite mark where it leaked and ran the paint, or a easily seen circle around an area such as a band stud nut or cooler line case fitting.
 
904 transmission pan gasket leaking anything I should know before pulling pan off and replacing gasket?
Check if your dipstick tube still has the single "0" ring type seal. When that "0"rings dries out the trans will leak.
Upgrade to the newer boot style seal that will never leak.
 
Get the rubber over metal gasket from the dealer for a 42RH or 42RE trans.
They seal really well and are reusable.
I know it's kind of a pain in the butt, but there is also a small metal plate that covers the output shaft bearing snap ring that is normally cork and leaks just under the trans mount.
These can look like a pan leak since it is so close to the pan.
(Just so you know it's there)
Hey TrailBeast, I am trying to hunt down a 904 leak that looks like its the pan but was not aware of the output shaft bearing seal. Is that accessible? How do I verify this seal is leaking or not? Thanks
 
Hey TrailBeast, I am trying to hunt down a 904 leak that looks like its the pan but was not aware of the output shaft bearing seal. Is that accessible? How do I verify this seal is leaking or not? Thanks

It's on the bottom side of the output shaft housing (and sometimes even under the trans mount)

housing.jpg
 
Yiks that looks like it is right on top of the transmount. I guess I could feel for seepage up there but I would not know how to teplace that seal if indeed it is leaking.

There is a plate with two large Phillips screws holding it to the housing with (usually) a cork gasket about the same size as the plate covering the slot.
In my experience cork ALWAYS leaks eventually, so I seal that plate to the housing with RTV only and they never leak again.
 
Yiks that looks like it is right on top of the transmount. I guess I could feel for seepage up there but I would not know how to teplace that seal if indeed it is leaking.
So looking at your red pointer I see drips coming from the two vertically stacked cast eye’s holes just below your pointer which looks like it could be that spot. Do you know the name or part number for that gasket?
 
Extension housing gasket? Those are a pain. I always silicone both sides of that gasket because there may be casting or machining flaws and the replacement gasket is thin.
 
And the Chrysler bean counter who approved the cost cutting measure of not having a drain plug in the pan should be shot.
 
So looking at your red pointer I see drips coming from the two vertically stacked cast eye’s holes just below your pointer which looks like it could be that spot. Do you know the name or part number for that gasket?
Those holes are for a factory floor shifter bracket. If the fluid is running down from the front of the holes it'd either the extension housing seal or the rear band shaft seal is leaking. To replace the rear band shaft seal you need to remove the extension housing and screw a 1/4" bolt into the pin and pull it out just far enough to replace the o-ring. Don't pull it out any farther than necessary to replace the o-ring or you'll let the rear band linkage fall apart inside
 
Those holes are for a factory floor shifter bracket. If the fluid is running down from the front of the holes it'd either the extension housing seal or the rear band shaft seal is leaking. To replace the rear band shaft seal you need to remove the extension housing and screw a 1/4" bolt into the pin and pull it out just far enough to replace the o-ring. Don't pull it out any farther than necessary to replace the o-ring or you'll let the rear band linkage fall apart inside
After replacing the speedometer housing seals twice and a nee pan and factory gasket which is now sealed well I am still leaking at that floor shifter baracket holes. I am not an expert on trans and want to know more about the two places you are referring to. So is the first place you are mentioning large tail assembly gasket? I was told this trans was rebuilt but I am starting to doubt it.
 
After replacing the speedometer housing seals twice and a nee pan and factory gasket which is now sealed well I am still leaking at that floor shifter baracket holes. I am not an expert on trans and want to know more about the two places you are referring to. So is the first place you are mentioning large tail assembly gasket? I was told this trans was rebuilt but I am starting to doubt it.
Yes and I rarely see them leak. It's usually the rear band pin seal and it'll look like it's the extension housing gasket. You wouldn't believe how many times I've torn apart transmission that were supposedly rebuilt only to find their idea of a rebuild was to just pull the clutch packs and install new clutch discs and slap it back together. Not saying that's what was done with yours but it could be
 
Yiks that looks like it is right on top of the transmount. I guess I could feel for seepage up there but I would not know how to teplace that seal if indeed it is leaking.

Seriously? Two nuts in the center of the crossmember hold the transmission mount. 4 bolts hold the crossmember in. Put a jack under the transmission, remove the aforementioned fasteners, remove the crossmember, then remove the two bolts that hold the transmission mount to the transmission then you are staring at the two phillips screws that hold the plat on. Remove those, remove the plate and replace the seal. reassemble in reverse order. Yikes?
 
Seriously? Two nuts in the center of the crossmember hold the transmission mount. 4 bolts hold the crossmember in. Put a jack under the transmission, remove the aforementioned fasteners, remove the crossmember, then remove the two bolts that hold the transmission mount to the transmission then you are staring at the two phillips screws that hold the plat on. Remove those, remove the plate and replace the seal. reassemble in reverse order. Yikes?
Hey RustyRat I did this. Yikes because I have 3 ruptured vertebrae and being on my back is difficult for me. I did this and also replaced the speedo housing seals twice. I also replaced the pan with a new one. I oowered thru this but I can’t begin to tell you how painful it was for me. I still leak and yikes I don’t think I can do anymore right niw as much as I want to.
 
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