Unserviced transmission question

2005 BUICK PARK AVENUE
120,000 MILES • 3.8L • V6 • 2WD • AUTOMATIC
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JACOBSLADDER
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Hello I purchased a 2005 Buick Park Avenue that my grandfather owned before he passed and have been putting some work into the suspension and after completely redoing everything I noticed the transmission fluid is super old and running brownish in color. The issue is I purchased a new filter, gasket, seal and fluid but now I'm hearing that if it hadn't been done don't do it because it will knock stuff loose and cause it to go bad really quickly. I understand where they are coming from but I can't simply let the fluid go completely nasty so what should I do? Thank you in advance and I really appreciate it!
Aug 27, 2025 at 5:38 PM
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CANNON1349
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Hello, this is common advice from those who went through a time where transmission fluid was mostly petroleum-based, much like engine oil. It deteriorated and became gunky, basically held the transmission together when it started to break down. That was well prior to 90's vehicles. In your 2005 it wouldn't be the same case, transmission fluid is overwhelmingly synthetic, and does not wear out, only becomes dirty. If you are unsure about the condition of the transmission fluid, please post a picture of the dipstick and/or the color of the fluid on a white paper towel. If it is brown without any red tint that would indicate clutch material was burnt at some point. However sometimes it is hard to tell if the color is just dark red or actually brown.

Please let us know,
William
Aug 27, 2025 at 7:21 PM
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MECHTRIX
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Every great operating transmission i ever saw had super clean oil in it ...so The oil should always be clean its whole life as close to new out of the bottle as possible .. that said
If you ask me it a myth that changing you oil will braek it theres alot of misconceptions going around I've been hearing that my whole life never seen it happen ever ..and if it did happen after changing the oil it was becuase they never changed it before poor maintainance and those transmissions where already broken or had other problems that were ignored" for a long time ..example" hey heres how to ignore and make it last.forever..just don't change the oil ever and tell yourself and everyone else to do the same or they're transmissions will all break if they change the oil ..makes no sense right ? Speaks for itself
So if your honest you already know what the answer is just ask yourself whats beter a dead transmission thats never had the oil changed or or a great one with brand new clean oil and a new filter in it ? Speaks for itseft right ?
Every great working machine required regular maintainance and got it .. fact . And every great running machine that ever lived a long life had it ..fact
You gotta change it somtime right ? Cant just ignore it or it will die much sooner ..fact
And if other transmissions broke right after changing the oil its becuase they didn't change it often enough before just drove around for months with dirty oil in it thinking it was somehow good for the transmission ..so just ask them what they did when it broke they all say oh I just bought a new one ...now I don't know about you but I'm not in the business of buying transmissions
I bet gramps would have agreed
Just change it see what happens and if its working good now with dirty oil it should work better with clean oil and filter right ? And last I heard its never crime to to do the right thing ..at least not yet nothing ever turned out good after doing the wrong thing fact
And if bad things happen along the way than do the right thing again and again .. makes sense right ? The longer you wait the to change it the worse it will get ..just enjoy your car and "be well "good luck
Aug 27, 2025 at 8:10 PM
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JACOBSLADDER
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Thank you William and Mechtrix I appreciate it and will post pictures tomorrow William thank you again. They were the last of my grandparents to pass away so wanted to keep the car in good condition but they didn't do much other than oil changes. Talk to you tomorrow!
Aug 27, 2025 at 8:28 PM
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CANNON1349
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Sounds good, just let us know.

William
Aug 28, 2025 at 4:33 AM
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MECHTRIX
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Thanks for asking best of luck to you
Aug 28, 2025 at 10:45 AM
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JACOBSLADDER
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Okay I took a picture of the transmission fluid on the stick again I really appreciate it guys thanks. Sorry it keeps telling me the file type is not supported from my phone I'll try to convert it sorry about this.
Aug 28, 2025 at 4:18 PM
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STRAILER
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Is this with the engine running with the car on flat ground? If so the unit is overfull.
Aug 29, 2025 at 4:20 PM
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CANNON1349
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Like Ken mentioned, the vehicle should be running in Park on a level surface. In any case this fluid has a reddish hue to it, and I would declare this to be good and able to be serviced. Only dropping the pan and inspecting the magnet will give a clear view of what is going on.

William
Aug 29, 2025 at 4:23 PM
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MECHTRIX
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Yep it needs to be in the the cross hach marks also when checking it keep the stick vertical it shouldn't be sideways because the fluid will run upward on the stick
Aug 29, 2025 at 5:06 PM
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JACOBSLADDER
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Thank you gentlemen I really appreciate it, your knowledge is extremely helpful I have all the parts to drop the pan and do a filter and fluid change I will give it a try you guys are the best!
Aug 29, 2025 at 5:47 PM
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CANNON1349
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Sounds good, feel free to snap a picture or two of the pan if you can see the bottom, or at least drain until you can see what is sitting at the bottom. If there is a fine metal paste-like material on the magnet that is normal. Any pieces bigger than that indicate a problem.

Please let us know,
William
Aug 29, 2025 at 5:56 PM
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MECHTRIX
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yes photos would be really helpful at this next stage good luck
Aug 29, 2025 at 6:33 PM