Trans fluid change through return line

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Mar 18, 2008
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KC MO
Looking at doing a pan drop and filter change in my 06 Lucerne. Ive seen some people unhook a return line at the radiator and run more fluid out but would there be any problems unhooking the return line at the tranny and running fluid out that way? Thought it might make less mess than up on top?
 
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Jan 20, 2013
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Ontario, Canada
Looking at doing a pan drop and filter change in my 06 Lucerne. Ive seen some people unhook a return line at the radiator and run more fluid out but would there be any problems unhooking the return line at the tranny and running fluid out that way? Thought it might make less mess than up on top?
How many miles are on the fluid?
 

JTK

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Aug 14, 2003
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Buffalo, NY
Does this GM have the solid lines w/ push lock at the radiator cooler? Like said, if they're crusty, you might not want to touch them. Other than that, a cooler line pump out will get the most old fluid out. I've done it on GM's of that vintage. They pump a lot out quickly, so you have to be ready for it.

Does Doorman make an aftermarket pan with a drain plug? That might be an option for you if you intend to drop the pan and keep the vehicle a long time.
 
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Winnipeg MB CA
I used to do this (unhook a line at the rad) regularly on our '97 Mazda MPV.

Had a translucent plastic jug marked for 4 US quarts, and would try to hit the mark so I could add whole bottles of ATF.

It worked well.

As @JTK suggested, I bought a Dorman pan with a drain plug for our Dodge van. It's definitely easier.
 

mbaker

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JTK, It does have the push locks but the radiator line is somewhat hidden under the core support, that’s why I thought removing it at the trans might be easier.
 

mbaker

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Look, I know re the **** factor, but cleaning the swarf off the pan, the magnets, and changing the ATF filter once in a while has a lot of merit. Dorman pan with bung, for between those pan-drips 👍...
I was going to do a pan drop/filter and cooler flush at same time
 
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Jul 16, 2020
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Does this GM have the solid lines w/ push lock at the radiator cooler? Like said, if they're crusty, you might not want to touch them. Other than that, a cooler line pump out will get the most old fluid out. I've done it on GM's of that vintage. They pump a lot out quickly, so you have to be ready for it.

Does Doorman make an aftermarket pan with a drain plug? That might be an option for you if you intend to drop the pan and keep the vehicle a long time.
This, a pan drop and filter will get out 7+ quarts.
 

mbaker

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Mar 18, 2008
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Just finished up, pan drop and filter and a little over 7 qts dex VI. Only issue i ran into was the plastic neck of the filter snapped but was easy to remove the rest and move on.
 
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Jun 21, 2009
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Missouri
This cooler line pump out used to be called the "Hoot" method. I did it at 25 and 50K miles on my 2003 Silverado that now has 62K miles. I used TES 295 Transynd fluid both times. I pumped 12 quarts through each time.
 
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Apr 5, 2016
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Texas
Looking at doing a pan drop and filter change in my 06 Lucerne. Ive seen some people unhook a return line at the radiator and run more fluid out but would there be any problems unhooking the return line at the tranny and running fluid out that way? Thought it might make less mess than up on top?
This cheap little hand pump does the job through the dipstick on my wife’s 2019 grand caravan. Sucks out 4 qts. Then I just switch the hoses around and pump the new fluid back in from the gallon bottle it comes in.
I have a couple cars where it won’t fit down far enough do to obstructions blocking the way. So it works in some cases and some not.
 

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