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  1. #1

    Default Thoughts on flushing rather than pan drop...

    I've heard people do not like flushing the transmission thru the transmission lines on the radiator. Why? Any input? I have had mine done in between pan drops, which is about 20K between flushing and a pan drop. My truck has now 115,000 mi. So what are any problems anyone has had with the flushing?
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  2. #2
    Master Mechanic SupplySgt's Avatar
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    Feb 2010
    Middle TN, displaced Okie


    Flushing is bad for a transmission. It's much, much, much better for a transmission if you drop the pan and change the filter while you're at it. It's not so bad on a newer tranny but my rule of thumb is if it has more than 50-60k miles, you're just trying to kill the transmission by flushing it. There's too many things that can break loose when you flush it that way. I'm a little more conservative than most but I did get 250k miles out of the original transmission so I obviously did something right.
    93 Suburban (Southern Slayer): TBI 350, 4L60E
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  3. #3


    ive read horror stories on the internet from people flushing. all the crap/gunk/shavings get jammed in places they are not meant to be. a flush cost more than dropping the pan cleaning it out, new filter and gasket. plus you personally will know the health of your trans. when you find whats inside it. aka cluth lining, metal, mine i did for around 45 bucks with a really good quality filter. do what you want but consider yourself warned.

  4. #4


    Had a friend of mine get his flushed and it blew a seal...then he had to have it rebuilt a few months later. He said that it was the worst choice he's ever made. x3 on doing just a pan drop and filter swap. Never can go wrong by doing it yerself. If you're worried about the integrity or cleanliness of the fluid, just swap it again a little bit later.

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  5. #5


    I had a flush done on my work truck a couple years ago (07 F250 5.4 gas) per my boss's instruction rather than dropping the pan, a week later driving down the interstate it felt as if the truck slammed out of gear, the cruise then revved the motor up, it slammed back into gear and the transmission blew its guts out all over I20..

    Drop the pan. LOL

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  6. #6


    Drop the pan and get disconnect the cooler lines, go get yourself a bottle of the flush, and flush the cooler heavily IF you're even going to flush it at all.
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  7. #7


    Thanks for all the feedback! Keep it coming! Here is one for all to ponder. It would be great to hear a GM mechanic's thoughts on this one.

    My mechanic at my work (diesel mechanic) has a 2009 or 2010 1500 and he is getting it ready for his trip to OBX, in a few weeks. Anyway he took it to our local GM dealer for his 50,000 mi service. He asked about servicing his transmission (pan drop with filter) and the lead tech suggested just a flush because the filter on his transmission (4L60E) is just a screen. In other words it has no type of element at all. So he had the flush done. That being said I would love to hear other GM tech's thoughts or even GM's protocal on servicing transmissions.

    Another question about seals blowing. Here is my experience Saturday at a local 10 minute oil change chain. I asked one of the techs at the chain as he was flushing my transmission, his thoughts of flushing. He responded he had a bad experience with it due to a seal blowing. I asked what seal, he said he didn't know. But he took it back, the tab was $300, which they supposedly covered. But here is the kicker. The machine (T-Tech) they use uses the transmission pump to pump out the old and pump in the new. That being said how is it possible to have a spike in pressure when in park at idle while the fluid is transferring. Oh asked another tech there and he said he has done his truck a few times with no problems.

    Lets hear more opinions or experiences please!!!
    Last edited by dedmon27; 04-09-2012 at 07:50 PM.

  8. #8
    Sr. Engineer
    Join Date
    Oct 2010
    Indianapolis, In


    I have never gotten a satisfactory answer about what exactly they were flushing it with and how is the last transmision they flushed with the machine not somehow contaminating mine. I don't see ten different machines for ten different fluids. I think you are asking for trouble if you do.
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

  9. #9


    Quote Originally Posted by ippielb View Post
    Drop the pan and get disconnect the cooler lines, go get yourself a bottle of the flush, and flush the cooler heavily IF you're even going to flush it at all.
    x7 (as of this writing) on just a pan drop a filter replacement. However, @ippielb has a good idea in that IF you're going to flush something, flush the cooler and its lines while it's disconnected from the system. Personally, though, I'd stick to pan+filter and actually had a discussion with a mechanic of 32 years about this very thing, today -- he said the same.

  10. #10


    I flushed both of my trucks and my wifes windstar. Never had a problem with any of them

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