Tranny oil change using the return line

[civic_matic_00]

Has anyone done the tranny oil change below? I usually just drain and fill from the pan. is the procedure below the proper way to flush the old fluid?

http://www.allpar.com/eek/atf.html

James Bottger wrote:

While it's much better for the transmission to change the fluid using the method in [the above] article than it is not to change the fluid at all, this method only replaces about half of the fluid in the transmission. The best thing to do is to change out ALL of the fluid, and this is also something a person can do themselves.

First, drain the fluid from the pan, just like you would using Mr. Macfairlane's procedure. Once you've replaced the filter, the pan gasket, and reinstalled the pan, you're ready for the next step.

Fill the transmission to the proper level using the proper type of transmission fluid. Then disconnect the return transmission line (the line in which transmission fluid flows from the transmission cooler back to the transmission), located near the bottom of the radiator. There's two transmission lines connected in this location, and the bottom line is usually the return line. Once the line has been disconnected, attach a clear piece of tubing to the transmission cooler, the same diameter as the transmission line, approximately 5-6 feet long, using the transmission line clamp to secure it.

Place the unattached end of the clear tube in a plastic, one gallon milk container and place it where it can be seen (like not under the car).

For the next portion of the procedure, make sure that the parking brake is set prior to continuing. Start the engine. The transmission needs to be put into "Drive" so the torque converter fluid is changed as well. Some transmissions will only circulate fluid through the torque converter only in drive. This especially applies to the electronically controlled transmissions. [Craig Sherman noted that Drive is needed for most transmissions, based on technical manuals]

After approximately 4 to 5 quarts (obviously, if it's more than 4 quarts, you'll have to turn of the engine, and fetch another milk jug) of fluid have been pumped out, you should notice a change in the color of the fluid. It should go from a brownish red color, to a bright pinkish red color. When this happens, all of the old fluid has been replaced with new fluid.

Be careful not to overfill the tranny during this procedure.

When completed, reconnect the transmission return line to the transmission cooler. Check the fluid level as you normally would, and add fluid as required.

This fluid change method is twice as good for your transmission as the method of only changing out half of the fluid is. Happy shifting!

[landspeed]

Sounds reasonable. I have heard of people doing this to change their oil - I suppose as long as you are careful to not rev the engine while doing it etc, it should be OK! My transmission doesn't have a pan or filter or anything, but I have thought up a modified method I could use. I will just take a look at my service manual and see...

[civic_matic_00]

Originally Posted by landspeed

Sounds reasonable. I have heard of people doing this to change their oil - I suppose as long as you are careful to not rev the engine while doing it etc, it should be OK! My transmission doesn't have a pan or filter or anything, but I have thought up a modified method I could use. I will just take a look at my service manual and see...

thanks landspeed!

[Otistheminivan]

Yeah we do that at work all the time. I know i've found that in a bunch of different cars repair info.

John

[Frankenstipe]

I'm going to do this either on my next change, 60k miles (at 33k now), or when/if I get a transmission cooler.

[GasSavers_Dust]

Been thinking about doing this, but I am a little too afraid of doing something bad to my tranny.

[GasSavers_archangel]

Not the way to do it!
The automatic transmission cooler lines only bypass cool, so some of the fluid is used to power the trans, and some goes to the cooler so after a while you will have some new fluid coming out with some of the older fluid, and at a point you will be getting as much old fluid as new fluid.

The only way to do it and insure that all the fluid is changed, is to drop/drain the pan and change the filter,then turn the flywheel until the torque converter drain plug is on the bottom and remove the plug to drain the converter.
Then reinstall the pan and converter drain plug and fill it 1/2 way with fluid, start the engine and add all but the last two quarts, check for leaks, then check the level and add some again and again until you get to the cold full level.

Yeah, a small amount will remain here and there just like changing motor oil, but that's the best, and the only "proper" way to do it.

[GasSavers_Dust]

That is true, only when you have a torque converter drain plug.

[mtbiker278]

For most Honda cars (toyotas too I think) the transmission doesn't have a pan to drop, or a filter you can change without pulling out the whole transmission.

My old 2001 civic's maual recommended draining the fluid and filling it back up through the dip stick hole (~2.5L) driving for 25-50 miles going through all the gears, and repeating this 3 times. The whole transmission fluid capacity was about 6.2L. If you do the math after 3 fluid drain and fills you'll have approx. 400mL of old fluid left in the transmission (6%).

Altrernatively you could do a drain and fill as part of your oil change or every other oil change. That would keep your fluid relatively fresh.

As for filling through the return line, I don't even know if my civic has a transmission cooler. Although I haven't really looked, I'm sure it would be pretty obvious.

[GasSavers_Dust]

I would think that it would be plumbed into the radiator. Might see if there is a few hoses at the bottom of the radiator.