Idea for ATF change

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I have the complete manufacturer instructions for an ATF change using the cooler line method but I was wondering if there was a better / easier way without getting under the car.

Since the recommended method involves running the system dry, I presume this is safe to do.

So the idea would be:

- extract as much as possible with Mityvac
- run the vehicle for x seconds (enough to fill the pan)
- perform a second extract

Depending on vehicle, this would give 60% to 80% changed in one shot.

Doing it twice would mean 85% to 95% change.

Anyone think this is a safe thing to do?
 
The pump draws fluid from the pan. If you've emptied the pan, it will suck air and pretty much stop pumping IMMEDIATELY after you start the engine- that would probably push at most another few ounces of fluid out of the torque convertor and passages, and potentially air-lock the pump.

I wouldn't recommend it- no real benefit.
 
Thanks

So I may do a hybrid method because the factory method still mixes some new with old:

- disconnect cooler line
- mityvac the pan
- refill
- follow regular instructions

I think this method minimizes mixing new ATF with old ATF that is left below the pick up.
 
Originally Posted By: 440Magnum
The pump draws fluid from the pan. If you've emptied the pan, it will suck air and pretty much stop pumping IMMEDIATELY after you start the engine- that would probably push at most another few ounces of fluid out of the torque convertor and passages, and potentially air-lock the pump.

I wouldn't recommend it- no real benefit.



Agreed, and there is potential to do harm since some parts will go without lubrication,

IMO, extract as much as you can, refill, drive 2-3k, repeat.
 
Originally Posted By: TrevorS


Anyone think this is a safe thing to do?


No you will fubar the pump. Just do 3 extractions.
 
Once you suck out the pan it will not refill. If the pump doesn't pick up any fluid it can't push any around inside.

If you first sucked the pan dry then added the recommended qts, then pump it dry at the cooler it would be what the factory method basically does.

I never had a problem with doing it the factory way. You might use an extra quart or so. The fluid doesn't really mix until it gets back to the pan.
 
Originally Posted By: TrevorS
I have the complete manufacturer instructions for an ATF change using the cooler line method but I was wondering if there was a better / easier way without getting under the car.

Since the recommended method involves running the system dry, I presume this is safe to do.



If you start dumping in fluid just as the flow from the line slows, then continue to do so till you've added approx three quarts less than a full fill(have all your bottles open, ready to go), you'll have almost a full change once topped off... Just watch flow as the fluid is added, once it slows after last quart, cut engine...

This is the method I've used for years, won't pull a pan unless I suspect a issue...
 
Originally Posted By: TFB1
This is the method I've used for years, won't pull a pan unless I suspect a issue...

You mean you just leave the silt in the pan and the fuzz on the magnet?
 
Originally Posted By: Kestas
Originally Posted By: TFB1
This is the method I've used for years, won't pull a pan unless I suspect a issue...

You mean you just leave the silt in the pan and the fuzz on the magnet?


Yep, you got it, let sleeping dogs lie...

I went this route after opening them up time after time and finding next to nothing, may not be a good idea on all brands but Ford RWD trans(all I'll own) won't have a issue...

A maintenance schedule was posted here that one taxi co followed and the trans??? They never serviced, just swapped out if failed...
 
Originally Posted By: TrevorS
Thanks

So I may do a hybrid method because the factory method still mixes some new with old:

- disconnect cooler line
- mityvac the pan
- refill
- follow regular instructions

I think this method minimizes mixing new ATF with old ATF that is left below the pick up.

I think this is the best way.
 
Originally Posted By: TrevorS
I have the complete manufacturer instructions for an ATF change using the cooler line method but I was wondering if there was a better / easier way without getting under the car.

Since the recommended method involves running the system dry, I presume this is safe to do.

So the idea would be:

- extract as much as possible with Mityvac
- run the vehicle for x seconds (enough to fill the pan)
- perform a second extract

Depending on vehicle, this would give 60% to 80% changed in one shot.

Doing it twice would mean 85% to 95% change.

Anyone think this is a safe thing to do?


I would think that once the pan is near empty, the pump will pick up air and do no pumping.
 
Originally Posted By: Donald
Originally Posted By: TrevorS
I have the complete manufacturer instructions for an ATF change using the cooler line method but I was wondering if there was a better / easier way without getting under the car.

Since the recommended method involves running the system dry, I presume this is safe to do.

So the idea would be:

- extract as much as possible with Mityvac
- run the vehicle for x seconds (enough to fill the pan)
- perform a second extract

Depending on vehicle, this would give 60% to 80% changed in one shot.

Doing it twice would mean 85% to 95% change.

Anyone think this is a safe thing to do?


I would think that once the pan is near empty, the pump will pick up air and do no pumping.


That's correct and why when you pump it out from the cooler hose the flow stops but the torque converter is still full.
 
Originally Posted By: SHOZ


That's correct and why when you pump it out from the cooler hose the flow stops but the torque converter is still full.


Which is why adding fresh fluid while engine is still running works as almost a complete change, fluid from pan is pumped into converter then out of the cooler line... Generally the converter holds 2/3 to 3/4 of the total fill...
 
I would not do it that way simply becasue it causes you to rush too much and you cannot get an accurate sense of what has come out.

The pump is a simple vane pump with sliding metal plates in an eccentric housing. No damage would occur for dry running for a few seconds.

If you pump the fluid out and then turn off the motor, then measure what came out, then compare that to what the capacity is, you know exactly how much to add back in. I would allow for at least a qt extra.

hydraulic-vane-pumps-work-2.1-800x800.jpg
 
I see no reason to do anything other than drain the pan and refill it. Doing this often, ensures clean and debris free trans fluid.

The "line method" simply empties the pan and then sucks 10 additional quarts of clean fluid and pumps it out of the line. Next time you try a line method, look at the color of the discharge. 4 quarts into the "change" the line fluid goes clean!

Put another way, the "line method" new fluid does not "go through all the parts", including the actuators, the torque converter, the cooler and so on, before it gets discharged. It simply pumps out of the sump.
 
No it definitely goes through the TC. The usual path is out of the TC and to the cooler and back to the pan.
 
Originally Posted By: Cujet
I see no reason to do anything other than drain the pan and refill it. Doing this often, ensures clean and debris free trans fluid.

The "line method" simply empties the pan and then sucks 10 additional quarts of clean fluid and pumps it out of the line. Next time you try a line method, look at the color of the discharge. 4 quarts into the "change" the line fluid goes clean!

Put another way, the "line method" new fluid does not "go through all the parts", including the actuators, the torque converter, the cooler and so on, before it gets discharged. It simply pumps out of the sump.


Not on the trans I've changed, fluid doesn't change color till approx the full fill has been pumped from the trans...

The fluid in my F-150 looked like 10K mi motor oil when I bought it and was horribly rancid smelling(my guess it had never been changed in it's 177K mi life)... After douching 12 quarts through it(it's approx dry fill) there is no color on the dipstick at all... And that's approx six months after the change, just checked it a week ago...

Also had same results when I changed the '98 Grand Marquis a couple years ago that had orig fill... It only had maybe 45K mi at the time so fluid wasn't horrid but still was far darker than new fluid...
 
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