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I've got an old 80 GMC Jimmy with a 350 th400 and lockers on 35's. I love it, she's a beat up cheap truck but had been very dependable and a beast New Years eve me and a couple buddies went out to ride this old coal mine in her and a couple jeeps. With a little trash talk i was talked into trying to drive through the corner of a mining pond. The clear water made it seem deceptively deeper than it looked. The second I hit the water and realized the motor was going under i cut it off. The water was high enough to flood into the cab over the bottom part of the seats.

It took us about two hours to winch her out. She was leaning starboard so only half of the motor was under water. I drained the oil (and about 2 gallons of clear water) changed the filter and pulled the spark plugs and it shot water out of the four cylinders on the right (that side had the oil breather under water). I checked the ATF before driving and after about a mile of driving and it looked good and red. We were way back in the woods and through some real rough stuff so towing it or trailering it wasnt an option.

After about 3 miles out of the woods and 4 miles on back roads back to my house i rechecked the ATF and it was pink and milky. I figured swap the fluid and filter and I probably hadn't taken too much life off the tranny but after reading around I'm a little worried. A few stories Ive read said any water in the tranny is a death sentence for it. That the friction plates were hydrophilic and the glue holding the abrasive would deteriorate very quickly.

Surely someone on here has sunk a truck and gotten water in an automatic. What did yall do and did it kill your tranny? Thaks for any input.
 
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Also, if you are sure that there is water in your transmission it is due for a service anyway. It means you have a faulty seal or oil line fitting. The viscosity of water is quite a bit different than ATF but I would still be surprised if there wasn’t a leak somewhere a properly serviced transmission should be able to submerge in water for at least a couple hours without seepage. If it were me I would pull it but an easier option would be to pull the pan and let it sit outside and drain for a couple days.
 

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Discussion Starter #4 (Edited)
I'm using tapatalk and it's not letting me post pictures or links. It says I have too few posts. I'll try after a few posts.

Yeah I'm sure the tranny needs some work, it's a pretty rough truck. I'm wondering if the dipstick was under water. Pull the pan and let it sit a few days? That long? What would you do if you pulled it? Rebuild or try to flush all the water out?


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Water through the dipstick seems like a good possibility and yes it takes a long time for a tranny to drain, a couple months ago I pulled the pan on a 47re from my dodge diesel and I wanted it to drain while still in the truck. It dripped for almost a week!! I couldn’t believe it and even after your tranny stops dripping it wouldn’t be empty because there is still fluid in some of the reservoirs and TC.

I would pull it, I doubt you need to rebuild it but a thorough cleaning would work wonders, there might not be a lot of water as it took a long time for it to cycle through and show on the dipstick so hopefully you wont have to replace anything.

I’m not an expert on the th400 so I wouldn’t know what to look for specifically but I would remove the valve body and spray it good with an air nozzle as for the friction plates take them out and inspect them. Should be fairly easy to see if something isn’t right. Buying new seals wouldn’t be a bad idea and look for grease patterns on the transmission to see where a leak would be if there was one.

Maybe someone with a better knowledge of the th400 will get on here and shed some light on the topic. In the mean time some pics of the truck in the lake would be awesome! I just joined the forum too I only have a few posts as well.
 

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Seals are not designed to keep water out. They are designed to keep ATF in. Whenever you submerge something like a transmission, a pressure differential occurs. Water being denser than air will have higher pressure than the air still inside of the transmission, and the water will try to push it's way into the transmission. In your case, that is exactly what happened as you ended up with pepto-bismo in the transmission. One likely place for water to get in is thru the bottom of the dipstick tube because most are just pushed into the case and use a simple O ring to seal it, and the O ring does a terrible job keeping water out.

Yes friction plates don't do well with water. If you can drain it all out before putting the tranny back in service, you might be OK, but the longer water is present in the transmission, the worse off you'll be. You'll know it's bad if you find junk in the pan. The hardest part of changing contaminated ATF is getting it out of the torque converter. The best option is a full flush

Ed
 

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Discussion Starter #8
Thanks all. I'm doing to start with a good flush and consider pulling abs and checking it out. Now I'm sure you've all heard people tell stories about changing fluid or flushing a tranny and it giving out in a few weeks. Why is that?


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It's a Chebby - take it back, and make it a reef habitat for Bluegills. :flipoff2:
 

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Pull pan off, drain for 20-30 mins, new filter, fill it up, run it around for a little bit then repeat until fluid clear. It will blow up, or it won't, most likely it will be fine. Worst case scenario, you spend $50 on tranny fluid and need to spend 200 more on another transmission.
 
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Seals are not designed to keep water out. They are designed to keep ATF in. Whenever you submerge something like a transmission, a pressure differential occurs. Water being denser than air will have higher pressure than the air still inside of the transmission, and the water will try to push it's way into the transmission. In your case, that is exactly what happened as you ended up with pepto-bismo in the transmission. One likely place for water to get in is thru the bottom of the dipstick tube because most are just pushed into the case and use a simple O ring to seal it, and the O ring does a terrible job keeping water out.

Yes friction plates don't do well with water. If you can drain it all out before putting the tranny back in service, you might be OK, but the longer water is present in the transmission, the worse off you'll be. You'll know it's bad if you find junk in the pan. The hardest part of changing contaminated ATF is getting it out of the torque converter. The best option is a full flush

Ed
Though you are correct a transmission seal is not meant to seal water, a transmission behind an engine that is off under only a few feet of water will not create enough of a pressure differential to suck in even more than a few drops through the tight rubber of a seal. The pressure of water at the top of a pond is not much more dense than the oxygen/nitrogen mix at our level in the atmosphere the transmission would have to be much deeper to create that kind of pressure differential.

It is also highly unlikely that water seeped into any point through the dipstick tube in this scenario because he checked the dipstick reading multiple times and did not find any “pepto-bismo” until several miles down the road. Any transmission that is installed and has working seals should be able to be submerged for at least a couple hours without any more than a drop coming through. The transmission most likely has a faulty seal or loose line fitting.
 

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Though you are correct a transmission seal is not meant to seal water, a transmission behind an engine that is off under only a few feet of water will not create enough of a pressure differential to suck in even more than a few drops through the tight rubber of a seal. The pressure of water at the top of a pond is not much more dense than the oxygen/nitrogen mix at our level in the atmosphere the transmission would have to be much deeper to create that kind of pressure differential.

It is also highly unlikely that water seeped into any point through the dipstick tube in this scenario because he checked the dipstick reading multiple times and did not find any “pepto-bismo” until several miles down the road. Any transmission that is installed and has working seals should be able to be submerged for at least a couple hours without any more than a drop coming through. The transmission most likely has a faulty seal or loose line fitting.
Or it came in through the case vent at the top of the trans.
 

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Drain, refill, take it on a long ride to get tranny hot and evap any residual water. Find a used th400 for $100, rebuild, then swap.


This. Rebuilding old transmissions is not that hard. Plenty of good resources online. Get a rebuild manual, clutch compressor and get to work on another used one. Once it's done swap them out and you'll be as good as new.


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Though you are correct a transmission seal is not meant to seal water, a transmission behind an engine that is off under only a few feet of water will not create enough of a pressure differential to suck in even more than a few drops through the tight rubber of a seal.
I' still have to disagree. We're not talking about deep sea diving here, but the basic physics still apply. Water has weight and mass and even a few inches underwater, the weight and mass of water presents itself as higher pressure to something with less density, such as air. Next, pressure differential doesn't "suck", it pushes. Pressure always "pushes" from high to low. Remember, water has weight. A transmission submerged in just a few inches underwater will have seals trying to resist several gallons of water…how much does each gallon of water weigh? And how much "water weight" can the seals resist if the other side of the seal only has the weight of normal air at atmospheric pressure?

The pressure of water at the top of a pond is not much more dense than the oxygen/nitrogen mix at our level in the atmosphere the transmission would have to be much deeper to create that kind of pressure differential.
Can't change the physics, water has weight and mass. Air is much lighter. The only way water won't enter the seals and into the transmission is if they are designed to withstand the weight of several gallons of water (which they are not) or pressurize the air inside the transmission.

It is also highly unlikely that water seeped into any point through the dipstick tube in this scenario because he checked the dipstick reading multiple times and did not find any “pepto-bismo” until several miles down the road.
If he shut off the engine immediately, the water and ATF didn't have a chance to mix. The water went to the bottom of the pan and the ATF floated on top of the water. It's possible that there wasn't too much water, and the OP didn't make mention that the ATF level was high. Later down the road with the engine running, what water was inside began to mix with ATF making "Pepto-bismo". Been there-done that

Any transmission that is installed and has working seals should be able to be submerged for at least a couple hours without any more than a drop coming through. The transmission most likely has a faulty seal or loose line fitting.
I wouldn't count on that theory holding water. Anytime you submerge a tranny, you take a huge risk that water will get in. First, you just don't know the condition of the OP's transmission or the condition of it's seals, nor could you say that about any transmission. Second, you just don't know how deep the transmission went under. Maybe you can be more confident with a rebuilt transmission with all new seals and few miles on the rebuild, but anything else won't apply. My basic belief I would strongly suggest that if you submerge the truck deep enough for the transmission to go underwater, get it out as quickly as possible. The seals aren't designed to keep water out and there are other places, in a transmission for water to get in.

Ed
 
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“Suck" can mean push or pull suck is more of an objective term in the way that I used it you could say the pond is sucking the air out. The thing that doesnt make sense is that an object placed in water isn’t subject to the entire weight of the water like you described especially not at the top of a pond.

Also “Can't change the physics, water has weight and mass. Air is much lighter. The only way water won't enter the seals and into the transmission is if they are designed to withstand the weight of several gallons of water (which they are not) or pressurize the air inside the transmission.”

This implies that water carries the same density. Water pressure drastically increases with depth and water at the top of a pond does not carry nearly enough pressure to penetrate a thick rubber seal designed to hold in hot flowing oil.

You can’t change the physics, oil on the other side of the same seal when heated up is a much more similar viscosity to water and in some places it is pressurized and it obviously contains the pressure of its own weight inside the transmission therefore there is no way that a little bit of pond water would be able to penetrate the seal.

By the way seals not only seal in oil and liquids like water, THEY SEAL IN AIR which is a gas that has a much much much lower viscosity than both of the latter. So you would be counting on the small weight of non moving pond water to physically move the lips of a seal.

Have you ever felt a seal? I seriously doubt it because it would take a significant amount of pressure to manipulate one. When you jump in a swimming pool you arent subject to all of the gallons that are around you? or on your level? or whatever you were trying to say? I don’t know what you are trying to say there lol it doesn’t make sense at all but apparently youve never been swimming before because you dont feel pounds of pressure on your skin in fact you barely feel anything at all.

I don’t know how the dipstick reservior is on a th400 but in most transmissions a dipstick wouldnt just go to the pan.. Also "The water went to the bottom of the pan and the ATF floated on top of the water” just because water has a higher density doesn’t mean it would sink to the bottom oil has a higher viscosity remember?? just because oil dumped on water floats on top doesn’t mean water dripped on oil will sink. Have you ever got coolant or water in an oil drain pan? you can see the drops right on the top of it. Some of it would go to the pan or elsewhere but most likely you would be able to see it on the dipstick.

"Or it came in through the case vent at the top of the trans.” I was unaware that th400’s didn’t have vent tubes..... also even if it doesn’t have a vent tube the case vent on transmissions are usually angled down making it very hard for water to seep in gravitationally unless in an extreme angle... which may have been the case here depending on which side its on.
 

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“Suck" can mean push or pull suck is more of an objective term in the way that I used it you could say the pond is sucking the air out.
You can use the term "suck" as an objective term….but it still wouldn't be accurate. "suck" in it's normal term would indicate the presence of a vacuum, which of course, isn't occurring.

The thing that doesn't make sense is that an object placed in water isn’t subject to the entire weight of the water like you described especially not at the top of a pond.
I'm not talking about depth….I'm talking about the mass and weight of water. This is entirely different. Even just an inch of water will still posses more mass and weight than the air above it. It won't be much, but it does exist. You experience that every time you pour yourself a glass of water. For every inch of depth you go, the pressure increases. Two inches under, and the pressure is going to be greater than one inch underwater. After a couple of feet underwater, the pressure is noticeable.

This implies that water carries the same density.
Density and pressure are two distinctly different things. You can easily "displace" a denser mass (water) with a lighter mass (air), if the lighter mass has greater pressure.

Water pressure drastically increases with depth and water at the top of a pond does not carry nearly enough pressure to penetrate a thick rubber seal designed to hold in hot flowing oil.
You're making broad assumptions. No seal comes with a depth rating, and seals wear as they are used. Maybe a brand new seal will hold out water at a depth of 6 inches, can you say the same for a seal that has been on a transmission for hundreds of thousands of miles, and exposed to miles of grime, and grit? Do you actually know the condition of the seals in the OP's transmission? Do you know the depth the transmission was submerged in? I would say you probably don't, which makes your response very and vaguely generalized, if it's even accurate.

You can’t change the physics, oil on the other side of the same seal when heated up is a much more similar viscosity to water and in some places it is pressurized and it obviously contains the pressure of its own weight inside the transmission therefore there is no way that a little bit of pond water would be able to penetrate the seal.
That would be inaccurate, my friend. Viscosity is not the same as density, and you simply can't heat up oil to be similar to the viscosity of water. Simple physics here is that oil is less dense than water and when both share the same space, oil will always float on top of water. It doesn't matter if it's a light oil like ATF, or a heavier oil, like 90 weight gear oil (which btw has a greater viscosity than water) it will float on top because it's less dense.

Next, yes ATF is pressurized, (and locally at the point where a pressure increase is required) ATF is not "pumped" to the seal, nor is the seal designed as a positive pressure seal, nor does it use oil pressure to seal. Further, besides ATF, air is also present inside a transmission, and this air mass is "vented" to the outside.

Now going back to some basic physics. The presence of a vent makes the job of a seal much harder to hold back water, why?… Any external pressure on the outside of a "container" can displace the air inside. Ever hold a glass upside-down in a sink full of water? Air gets trapped in it, right? Why doesn't the water flood the glass from the bottom? Because the air takes up space. What if the glass had a small hole in it? Water floods the glass…why is that? Because now the water can displace the air thru the hole. Transmissions are vented and they would act much like an upside down glass in a sink full of water, with a hole in it (and you may note that sinks aren't very deep)

By the way seals not only seal in oil and liquids like water, THEY SEAL IN AIR which is a gas that has a much much much lower viscosity than both of the latter. So you would be counting on the small weight of non moving pond water to physically move the lips of a seal.
You just destroyed your previous point that the seal is pressurized by the oil……

Have you ever felt a seal? I seriously doubt it because it would take a significant amount of pressure to manipulate one.
Do you know me? Do you know my experiences? And what do you know? Do you know the depth rating of any of the seals? Do you know the depth rating of any of the O rings that seal up the linkages, dip stick tube, speedo cable, or the pressure rating for any of the electrical connections?

When you jump in a swimming pool you aren't subject to all of the gallons that are around you? or on your level? or whatever you were trying to say? I don’t know what you are trying to say there lol it doesn’t make sense at all but apparently you've never been swimming before because you don't feel pounds of pressure on your skin in fact you barely feel anything at all.
Well, considering that I owned a swimming pool for the last 15 years at my old house, and ground breaking for the next swimming pool at our new house begins in about a month, or the fact that I've dived in the Caribbean, and snorkeled in Florida's natural springs and I'm an amateur underwater photographer, I think I know a thing or two about swimming and the effects of pressure. And BTW, I can feel pressure even in a few inches of water. You can usually tell in your ears.

Oh one more thing, since I live in Florida, most of our off roading usually takes place in water. I've dunked a few transmissions and I've drained my share of Pepto-Bismo out of them. Some of them had water in them being submerged in only a few inches of water (and they had good seals, or at least they didn't drip ATF)

The point however is, transmissions and water doesn't mix. You can never count on keeping water out because the seals were never designed for that. The best option is not to sink your truck so deep that the trans floods, but if you do, recover it as soon as possible and if you can, flush the fluid immediately. A couple of those transmissions I've flooded, went bad and required a rebuild, but if you drain them out immediately, you can save them. If you're mixing up Pepto, your trans doesn't have long to live.


I don’t know how the dipstick reservior is on a th400 but in most transmissions a dipstick wouldn't just go to the pan.. Also "The water went to the bottom of the pan and the ATF floated on top of the water” just because water has a higher density doesn’t mean it would sink to the bottom oil has a higher viscosity remember?? just because oil dumped on water floats on top doesn’t mean water dripped on oil will sink. Have you ever got coolant or water in an oil drain pan? you can see the drops right on the top of it. Some of it would go to the pan or elsewhere but most likely you would be able to see it on the dipstick.
Most dipstick tubes are pushed into the case, just above the pan, so any ATF you pour in will go directly to the pan. Most dip stick tubes are simply pushed into the case and sealed via an o ring (the tube is also bolted to some point to keep it from coming out of the case) If the water is deep enough, it could enter thru the opening at the top, but it can also enter at the o ring. If water gets in, it will go to the bottom of the pan regardless of it's "viscosity". You can experiment this for yourself. Get a glass container, pour in some ATF and pour in some water, the water will go to the bottom (even drops of water)

Ed
 

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Discussion Starter #18 (Edited)
Every where I've read about flushing the trans uses the supply and return lines from the cooler. I don't have a trans cooler. Can I just leave the pan off and turn the motor over till it quits pouring to drain torque converter? The just put the pan back on with a new filter and fill it back up? Or will running it dry burn it up?


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I'm not reading that its way to long, I was installing some axle seals yesterday and I was pushing on it to see how much force I could get it to move. It took about 4lbs of force (according to the equivalent on a food scale) to push in one point with my finger. Divide that around however large of an area it would take for water to move it in the manner that liquid would (larger surface area than my finger) that would and that doesn't even come close at all to what the pressure of water is and when a seal is installed ITS PRESSING AGAINST STEEL much stronger than standing alone. No way a seal would have any movement with the amount of pressure in a couple feet of water. Period.

Look you seem like a smart guy I just think you had a huge brain fart as there is no way in hell that tiny bit of force would manipulate a tightly fit rubber seal pressed against steel.

As for everything else I may be wrong the water it obviously leaked somewhere and until he can determine where exactly it came from its still a good idea to replace seals.

Jimmy256 you cant turn an engine over to get the fluid out of a TC it will just continually rotate to the bottom you have to remove it. Are you sure your tranny doesn't have a cooler? When I bought my blazer the engine and trans were removed but there was still a tranny cooler in front of the rad next to the condenser. My cummins has two of them one next to the engine that uses coolant.
 

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I love how this turned into a fluid dynamics discussion lol!
Anyway, so you all are properly informed, water weight, or head pressure as it's called, is .41 lbs per sq inch, per foot of water depth. So at 2 feet of water depth, the pressure is .82 lbs per square inch. Very little when it comes down to it. The heat inside the transmission will create higher pressures than that very easily. So to create the seemingly required 4 psi to circumvent the seal, you'll be at over 10 feet of water, considering the trans is at least 2 feet off the ground. My assumption is that the water either came in from a faulty seal, the dip stick tube seal, or the vent doesn't have a tube on it, and because the trans was allowed to cool down, the water could easily seep in even with the downward pointing vent tube. Run this mother fucker until it blows already....drain the fluid, fill the fluid, run the truck for a while, drain the fluid, fill the fluid, run the truck for a while, check the fluid again. Repeat the process if you keep getting milky fluid. Having fun is expensive, especially if you're stupid....
 
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