Homemade transmission fluid exchanger?

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SecondMonkey

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Last night while I couldn't sleep I was thinking about maybe trying to make a transmission fluid exchanger that would work as well as those machines they use in a shop. I was thinking I could take a 4" peice of pipe a few feet long, and put some kind of piston in the middle that would slide up and down. I could then fill it with clean fluid, hook it up to my transmission, and have the dirty fluid push on the piston which would inject clean fluid out the other side. I'd need some kind of bypass valve so it could circulate as normal after the fluid runs out.

Has anybody ever tried such a thing? Think it would work? What kind of oil pressure does a transmission normally operate at?
 
Hey, that's a pretty good idea.

The bypass could be simply a relief valve that opens at a little more than the DP that is required to move the piston.
 
What happens when the piston gets all the way to one side, and the pressure keep coming from the other? No flow, and a wrecked tranny.
 
Originally Posted By: mechtech2
What happens when the piston gets all the way to one side, and the pressure keep coming from the other? No flow, and a wrecked tranny.

That would be the point of the bypass valve.
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What I do, and Ive never had a problem with it is I disconnect a trans cooler hose, stick it in a gallon jug, turn the car on, fill up the jug to a certain point, turn the car off and put the same amount of clean fluid back in. Repeat until fluid is clean.
 
Quote:
I was thinking I could take a 4" peice of pipe a few feet long, and put some kind of piston in the middle that would slide up and down.


I've seen older machines that are exactly as you describe. They use a clear cylinder ..maybe 6" or more in diameter. It's the exchange machine version of the bouncing balls in the gas pump of yesteryear.

Your dream is only a decade too late..but it was still a good dream. Now if you can manage to fab it up for $25 or less you could probably put one in every BITOG members garage ....and most shops that don't have one due to the ridiculous cost of the legit ones.
 
I had one for removing fluid when accidentally topped off too much. It was a glass jar with metal lid. The lid had two big vacuum hoses. One hose went down the dipstick tube and the other went to a vacuum source on the motor. You obviously had to remove the line from the dipstick tube before the jar filled up to avoid sucking the fluid into the intake. Worked very well but required the engine to be running.
 
How much time would it actually save you over the normal method of a cooler line flush DIY's do at home? I would think what little it would save you would not be made up for the time put into buying parts and building it for a very long time. Cool idea anyway and if it was a clear pipe it would be a fun thing to watch. It might be worth it for the novelty factor.
 
Remove the cooler line and stick it in a empty bottle.Run the engine and remove 2qts,shut off engine add 2qts...repeat until the fluid runs clear.Purdy easy if you ask me and no risk of damage from running anything dry.
 
I used to just pull the line at the radiator and let it pump out while filling and moving the lever. 3 person job that requires some skill to fill fast enough, but it does work.
Now I have two automatic machines from Harbor Freight. Connect the right adapter and follow instructions. 20 to 30 minutes for the whole thing. It even filters the new oil going in. Better than sliced bread.
 
Originally Posted By: WishIhadatruck
How much time would it actually save you over the normal method of a cooler line flush DIY's do at home? I would think what little it would save you would not be made up for the time put into buying parts and building it for a very long time. Cool idea anyway and if it was a clear pipe it would be a fun thing to watch. It might be worth it for the novelty factor.
It wouldn't really take long to make - a chunk of pipe, some caps, and a piston in the middle. (not sure what for the piston yet - maybe an engine piston) I think it would be a lot better for the engine than stopping and starting several times to exchange it all, plus no measuring. I already looked into clear PVC but it's $35/foot.
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Originally Posted By: widman
Now I have two automatic machines from Harbor Freight. Connect the right adapter and follow instructions. 20 to 30 minutes for the whole thing. It even filters the new oil going in. Better than sliced bread.
Why the heck do you need two? For $700 I think I'd rather just never change the fluid and buy a new tranny when it dies.
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You'll need to get seamless pipe (and possibly controlled bore) and manufacture a piston (with an o-ring seal).

Maybe check out one of those places that the myth busters frequent to find an old double acting hydraulic cylinder.
 
Originally Posted By: Shannow
You'll need to get seamless pipe (and possibly controlled bore) and manufacture a piston (with an o-ring seal).

Maybe check out one of those places that the myth busters frequent to find an old double acting hydraulic cylinder.


Hmmm....I was thinking more like a peice of PVC pipe and possibly a plastic piston wrapped in leather. Wouldn't that work? How much pressure is a normal transmission putting out, anyway?
 
Originally Posted By: SecondMonkey
Why the heck do you need two? For $700 I think I'd rather just never change the fluid and buy a new tranny when it dies.
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Maybe he has more that one transmission.
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Hmmmm....instead of a piston, why not a bladder? The new fluid would sit in a plastic badder that was contained in your pvc cylinder with no air spaces between the bladder and cylinder. As the old fluid is pushed into the cylinder (outside of the bladder), the new fluid would be pushed into your tranny.
 
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