Change AT fluid question

Why not let the transmission pump it out for you?

Disconnect BOTH trans lines going to the radiator. Do both. Depending on the type of car, the pressure side could be the top or bottom fitting on the radiator

Run some flexible hose from these to an adequate bucket to catch the used fluid. Make sure that the hoses are toward the top of the bucket. You don't want to start sucking the used fluid back into the trans.

Start car and let it idle. The pump in the trans will empty most of the fluid into the bucket for you.

Make sure you STOP the engine AS SOON AS the fluid slows to a trickle. You don't want to run it long without fluid.

Measure the amount of fluid in the bucket. This is how much you need to replace.

Re-connect the trans lines to the radiator and fill the trans with the same amount you collected in the bucket.

Start engine, run trans thu all gears, and check level and for leaks, and your done.

Anybody have an easier way?

Thats the basics, but a couple comments. Drain as much ATF as you can first. This will get the mud out of the bottom of the tranny (do it while the ATF is hot). Measure how much you removed. Replace the plug. Add two quarts of fresh ATF and start the car. Leave it in Park and watch the ATF get pumped into your container. As soon as you see air bubbles, turn off the car. Measure how much you pumped out. Add two more quarts and start the car again. Keep repeating this process until the fluid getting pumped out is nice and clean. Keep track of how much you've added and how much you drained/pumped out. Reconnect the cooler hoses and add as much ATF as is necessary to equal what you removed.

You will use 4-6 extra quarts of ATF this way, but it will be clean.

John

I drain and refill mine 3X times (drain plug) to achieve ~ 95 % new fluid, I drive several miles between each of the 3X changes so the new gets mixed. I hesitate to remove hoses and clamps for a flush as it can introduce leaks later on. I use a new sealing washer on the final drain/refill. Eddie

I tend to agree with Eddie's philosophy and use this approach on 97 Legacy, but now I am planning to switch to synthetic ATF on WRX and mixing new synth and old dino does not seem right. On other hand, wasting 4-6 quarts of synthetic at $8/quart by pumping it until 100% new is excessive! Any suggestions about switching to synthetic ATF without cross-contamination and wasting 4-6 quarts?

"David Spektor" wrote in message news:...

Two things:

1. What is the millage? If this is the first change and the tranny has a large amount of miles on it (being a 97, I'm guessing that it's pushing 100K if not past it already), then you may wish to think twice about changing/flushing your transmission. A problem that is sometimes encountered in performing the first drain/flush on a transmission with high millage is that crud that has natrually built up in the transmission will be dislodged from a semi-harmless place in the transmission and proceed to travel to where it can impeed fluid flow and/or cause wear or other issues with various AT parts. You can search around on Google for cases of this and warnings of this and determine if the proceedure is worth it to you.
2. Automatic transmission fluid does much more than any other fluid in your vehicle. The fluid serves three purposes: Hydraulic drive/shift control, general lubrication, and cooling. Thus allowing the transmission to run with low fluid or without fluid is akin to running your engine without oil, coolant, and your power steering without fluid all at the same time. Needless to say, in that situation, more damage will be done than any good you were trying to do. Most synthetics are compatible with dino fluids, so the first suggestion of drain, add, drive, and start the whole process over again is a safe suggestion. Synthetic typically has a "cleaning power" above and beyond normal dino fluid. So in doing the drain/fill/drive routine over the course of a couple of weeks or so will give you a chance to get some of the crud and other things that may have been "cleaned" off of parts out of the transmission in the process. If you must use the flushing method, then use this process. Take TWO buckets. Make sure one of them is clean enough to eat off of. Fill the clean one with the new fluid you are wanting in your transmission. Be sure to put more in the bucket than your transmission will need (two extra quarts is a good saftey measure. Disconnect the fluid ouput hose (the line that carries the fluid from your tranny to the cooler) from your transmission cooler input and place it into the empty bucket for the old fluid. Disconnect the return line from the transmission cooler (the line that carries the fluid back to the transmission) and rig a piece of hose long enough to reach the bottom of your bucket with new fluid. How you rig this isn't important, but make sure it's a tight fit and will allow a consistant flow of new fluid into the tranny. By now you can probably see that it's a two person job. Once you have things set up and have checked everything, have the second person make sure the car is in neutral (wheels blocked of course for saftey). Then have them start the car. Allow the old fluid to be pumped out and the new fluid pumped in to replace it. Stop the car when you are about out of new fluid in the bucket. Reconnect the hoses. Check the fluid level and top off as needed. Start the engine up and let it idle while you check for leaks. Drive it slowly to check the opperation of the tranny and re-check for leaks. Then take it out for a normal drive (including some hi-way time) to make sure all is ok, and re-check for leaks. That should get you as near a complete fluid change as you can get while not sacrificing the tranny while you are doing it. As always YMMV.

Good luck, Jeramy

One more thing.. If you find that you are pumping fluid out, but nothing is getting pumped back in, then the proceedure that I gave isn't going to work. I ran into situations where it would work, and had one where it wouldn't. I should have mentioned that in my first post. :) Another note, I hate ATs.. as a personal pref. So I drive own and drive vehicles with MTs, and haven't had the misfortune to have to work on a AT in a while (last AT I worked on was a '97 tercel in 97). As always, take advice on here (including mine) with a grain (or a metric ton) of salt, and do what you feel comfortable with. In the end, that will result in you feeling better about your vehicle and cause you to enjoy it more. That's all that really matters. (This can be applied to pretty much all threads in auto groups like "which brand of oil is best?" or "which brand of filter works better?" etc.) I am sure some really anal people will disagree with me, but that's life. YMMV (your millage may vary)

Best wishes, Jeramy