Change AT fluid question

[Dan Chirica]

Hey Guys:

Is this a good idea? I want to change the AT fluid with synthetic
(Mobil1). I know if I drain the fluid myself only a fraction of the
total will drain. I was thinking to replace it (partially) with
synthetic an repeat the process several time until, hopefully, the AT
fluid is mostly synthetic.

Also is there a synthetic differential oil? What good brands of
synthetic At fluid and diff. oil are there?

Thanks. Sincerely,
Dan

PS: I apologize if this subject has been discussed before I couldn't
find any references, though.

 

[Edward Hayes]

I use Mobil1 synthetic in both my differentials and in my AT with excellent
results for 62,000 present miles. For the auto which holds 9.8 quarts your
first drain/refill of ~ 4.2 quarts will change ~ 1/2 the total. I change
mine three times driving ~ 1-200 miles between each change. This will give
you about 95% new fluid. I then change only one drain/refill every 10-15,000
miles. eddie

 

[Skweezieweezie]

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?

 

[Fred Flintstone]

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

 

[David Henderson]

How good can it be to run the tranny with little or no fluid?

 

[Edward Hayes]

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

 

[David Spektor]

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?

 

[Jeramy and Melissa Ross]

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?

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

 

[Jeramy and Melissa Ross]

Two things:

<SNIP>

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