Homemade Transmission Flush Machine

I know that this is going to sound extremely ghetto so try not to laugh too hard :). My friend wanted to do a complete flush of the transmission fluid on his 2000 mitsubishi galant but does not want to pay the extraordinary prices that most shops will charge for such a simple task. We brainstormed some ideas on how to make an extremely crude homebuilt flush machine. When I say extremely crude, I mean extremely crude. I just wanted to get some input on this "machine" and see what others think it's effectiveness will be. I was going to pull the return line from the transmission cooler and put it into a large bucket to drain the old fluid. As for getting the new fluid into the transmission we had two ideas. The first was to take a large container, drill a hole in the bottom and attach a hose. This hose would connect to the location that the return line from the cooler would normally attach to on the transmission. Our theory was that as the old fluid was pumped out the new fluid could drain back into the transmission provided that the container with the new fluid is held up above the connection so gravity would be doing the work, kind of like coolant exchange machines do. The second idea was to still disconnect the cooler return line but instead of feeding new fluid in via the cooler return connection on the trans we would drain out about a quart of fluid, stop the engine, fill the trans with a quart of new fluid via the dipstick tube and repeat till we get clean fluid coming out. What do you guys think? Thanks!

I would try to use some kind of pump (manual or electric) instead of gravity to force the fresh transmission fluid into the line. Can't help but thinking about MacGyver ever since I read your description... :rofl:

Ironically I've been watching a lot of macgyver lately because I've been going into work later. :grinyes: I forgot the name of the episode but at the beginning macgyver is in a car which loses its brakes. He tells the driver to pop the hood, he crawls out onto the front of the speeding car, disconnnects one of the power steering lines and uses the power steering pump to force fluid into the brake master cylinder so that the car could stop. It was a few days after this that my buddy asked me if I could help him with the trans flush and I had this episode in the back of my head when came up with the idea :). I guess I'm the Macgyver of the auto world now!

I did it once with a 5-gallon bucket of tranny fluid. I took the lines off the radiator and used some 3/8" fuel hose. I set the bucket of fresh fluid on the radiator, started a siphon of fluid out of the bucket and put an empty bucket under the other hose. Seems to have worked nicely. I just ran it until the stuff coming out was clean and red.

Hello, (Just in my opinion)...

I would have to agree with "Phoenix1" quote.

Phoenix1 quoted " I would try to use some kind of pump (manual or electric) instead of gravity to force the fresh transmission fluid into the line."

Years ago (about 9 years) when I did tranny flushes @ the place I worked at, (oil change shop) the machine had a pump in it and you could control the amount of pressure. See the tranny pump runs faster than gravity. I think eventually the tranny would run dry before enough fluid could be pumped back in. Don't get me wrong, you have the right idea. Your second idea is safer but will require more work and fluid. I have no idea what tranny flushes cost today, but weigh the cost and time compared to having it done in a shop.

Just my opinion. Let us know what you do or did...

Good luck....

Rev. AC

I've heard a tranny flush referred to as one of the bigger ripoff's that a shop can do to you... So I don't think its worth it IMHO, alot of vehicles go to the grave w/o even changing the tranny fluid

My .02$

Thanks for the advice about the pump. I think I'm just going to go with the second idea and drain/ refill by one quart at a time. I think it would be too complicated to build a system that could pump in the same amount of fluid that gets pumped out (I don't have the tools or the time/money). I called around to a couple of quick change jiffy lube places and the cheapest price I got was 70 bucks but the problem is that they can only fill their flush machine with fluid that comes out of the transmission fluid gun while the mitsubishi requires a special type of fluid (I believe it's called 3diamond type something or other...) so the only other alternative is to go to a dealer or AAmco, which will both cost around 125 bucks. If I do it myself it will only cost me 50 bucks for the fluid. The same holds true for my nissan altima. I want to switch completely to mobil one synthetic trans fluid. My only question is about the transmission cooler circuit. I am unsure of the path the fluid takes. I am assuming that the supply to the cooler comes from the torque converter and the return from the cooler drains back into the pan. The only reason I'm worried about this is since I will be draining the return from the cooler into a bucket; I don't want to be starving a vital part of the trans of fluid, like the valve body. If anyone could help me with this I'd appreciate it. thanks!!

I agree with the originally proposed/curtis73 solution

you NEVER want to "force" fluid into a transmission. I've heard of some nasty tranny disintegrations within a few hundred miles of such "power flushes"