Transmission Flush vs. Drain and Fill

[Shorehunter99]

Ok i have searched and searched and found conflicting opinions on this topic here. I recently bought a 97 3.4 v6 4runner with an auto tranny. It has 166 k miles on it and runs like a top so far. I am in the process of draining and refilling all the old fluids. Well i noticed the transmission fluid is dirty and definitely due to be replaced. I decided to drain it, drop the pan and replace the old filter in the tranny. I followed this write up here Dropping Pan And Flushing Transmission I also installed a B & M super cooler to bypass the stock tranny cooler and avoid the pink milkshake worry. Well i finished all this up last night and i filled the tranny back up with the same amount of fluid that i drained out, i decided to go with Mobil 1 syn which is what i have always used in all my vehicles. I let the truck sit over night so the gasket can fully cure before i start her up. My question is should i now proceed to "Flush and Fill" the tranny using the method described in write or should i just drain and fill again after a lil driving around? I know you can mix stock tranny fluid with syn but i really wanted to get all that old fluid out of there. Ive read that the flush can cause problems with higher mileage transmissions. I wont be using a machine just pulling the return line off the super cooler and starting her up letting no more than 1 qt. a time drain out then refiill and repeat till the fluid is bright red. This forum has been a huge help so far for me since this is my first toyota. Thanks for the help.

 

[shadow247]

If you disconnect both tranny lines you can do a flush pretty much like the dealership does it. Just get a gallon jug, fill it up with your ATF, place the return line from the trans into the jug, place the output from the trans into a different bucket. Start up the motor and keep an eye on the new fluid, once it gets low, kill the engine, refill your jug with fresh fluid, and go again. A few times of this and you will have flushed the entire transmission.

 

[audiness]

The purpose of the flush is to get the fluid that is stuck in the torque converter out. So you drained the pan, but theres still a lot of fluid in the converter. Also how was the condition of your filter screen? Anything in there?

 

[Shorehunter99]

The filter screen looked ok not much on it. The magnets had sludge accept one magnet also had some fine metal shavings on it. The fluid was brown and gross. I found the dealership the truck last resided at and called their service dept to get a run down on maintenance for this truck. I had regular oil and tranny fluid changes but never a flush.

 

[jkoni426]

I just flushed mine with 215k miles and unknown service history using the cooler line method and no problems. Don't be skurred!

 

[Steve240]

If you disconnect both tranny lines you can do a flush pretty much like the dealership does it. Just get a gallon jug, fill it up with your ATF, place the return line from the trans into the jug, place the output from the trans into a different bucket. Start up the motor and keep an eye on the new fluid, once it gets low, kill the engine, refill your jug with fresh fluid, and go again. A few times of this and you will have flushed the entire transmission.

Is there a link to a walk through for this method. It seems pretty straight forward. I have a question though, does the jug with new atf fluid have to be gravity feed into the trans or does the transmission have suction to pull it out of the jug?

 

[LittleCaesar]

Is there a link to a walk through for this method. It seems pretty straight forward. I have a question though, does the jug with new atf fluid have to be gravity feed into the trans or does the transmission have suction to pull it out of the jug?

I have never seen this method work, but it would seem to be the best way to go.

The bucket dump and 2qt fill though the dipstick at a time method has worked for me for fifteen years.

 

[nissanh]

I have a question though, does the jug with new atf fluid have to be gravity feed into the trans or does the transmission have suction to pull it out of the jug?

Do you keep the bucket with new oil above the engine level or on the ground?

 

[shadow247]

Do you keep the bucket with new oil above the engine level or on the ground?

Not sure, I have never done this method myself. I have only read and heard of others using it.