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  1. #1

    Default High Mileage Transmission Fluid- To Change or Not to Change

    I have 150K on my truck and have never changed the tranny fluid. I have always been told that if you go past the 75K mark then dont change it at all or the detergents in the new fluid will fail the seals and the tranny will go out. I actually had that happen to my 96 Tahoe back in the day about 2500K after a fluid change.

    I have read where some say that changing the tranny fluid for the first time at high mileage is OK as long as they drop the pan and do NOT use the "changing machine".

    What are some thoughts on having this done now or just leaving it alone?

    Thanks
    Jason
    2005 Chevy 1500 Z71 Crew Cab

  2. #2
    Master Mechanic silverhobey's Avatar
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    Default

    I have also heard that you should only use a flush machine if your tranny has had it regularly. If the tranny pan and bolts are in bad shape, I know guys who have just used a pump down the fill spout to get the old tranny fluid out. This way, you are not disturbing the gasket/pan area. This will not let you change the filter however. Tranny's aren't cheap if nothing works, and if you try something and it makes it worse (this is called Murphy' Law)
    (you should consult a Tranny Shop for 'free advice'..

  3. #3

    Default

    Dont bother changing it if it over 100k the small metal shavings are holding everything together... at my shop we wont do a tranny flush if its over 100k and has never been done on it.

  4. #4

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    Typically my modo for vehicle maintenance is run it until it breaks and fix only what is broken, with the only exception being I do change engine oil & air filters regularly. I've owned older cars with fairly high mileage so "run it" approach seems to work.

    My truck is an 05 and has 85k and was thinking about doing the 100k service, which includes the transmission fluid change. I think the manual states the first fluid change is at 100k.

    I've heard before not to change the fluid in the tranny but I was going to give this vehicle a shot at some PM prior to failure.

    Jason, is the truck in good shape and appears it's going to last another 50k+? seems like a change would be good, if not I'd leave it alone.

  5. #5
    Jr. Engineer
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    Changed mine this past summer with 109K miles on the truck. The gasket on the pan was like new, so I didn't replace it, just added some high temp silicone to it.

    I just dropped the pan and replaced the 5 quarts, filter and threw in a bottle of Lucas Oil Transmission Fix. The pan was very clean, not many shavings at all and my fluid was still fairly red. Now, 6,000 miles later it's still goin strong. I'd say if your fluid is starting to get darker or looks a bit brown or smells burnt, change it.
    SEAFOAM, I PUT THAT @#!$ IN EVERYTHING!



    2004 Silverado LS 5.3L Z71 Crew Cab
    260,000+ km

  6. #6

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    Change it.
    When you hear hoofbeats, look for horses not zebras.

  7. #7

    Default

    i have my tranny flushed every fall and add a bottle of Lucas Oil to it everytime. My tranny has 226k on it and is runnin strong... I'd change it. Prementitive matinance is always a good idea.

  8. #8

    Default

    Quote Originally Posted by pmason View Post
    Typically my modo for vehicle maintenance is run it until it breaks and fix only what is broken, with the only exception being I do change engine oil & air filters regularly. I've owned older cars with fairly high mileage so "run it" approach seems to work.

    My truck is an 05 and has 85k and was thinking about doing the 100k service, which includes the transmission fluid change. I think the manual states the first fluid change is at 100k.

    I've heard before not to change the fluid in the tranny but I was going to give this vehicle a shot at some PM prior to failure.

    Jason, is the truck in good shape and appears it's going to last another 50k+? seems like a change would be good, if not I'd leave it alone.
    Thanks for the comments everyone. The truck is in very good shape and has otherwise been maintained very well. Don't know why I let this one slip.

    The transmission seems to be running fine. It does have what feels like an occasional slip when accelerating slowly from a stop. It has been doing that almost since it was new though. Maybe twice a month? Obviously I put on some miles too.

    I have not checked to see how the existing fluid looks. I do have the Transmission Cooler so I assume that would have helped extend the life as well.

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