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GMC Transmission Fluid

Discussion in 'Chevy Trucks' started by J.onathan, Jan 22, 2016.

  1. J.onathan

    J.onathan Junior Member
    Messages: 25

    Hi All!

    I have a 2006 GMC Sierra 1500 4x4 5.3L (4L60E auto) that I recently put a plow on and started doing some plowing, we've only had a few snow events. The truck has 260,000km (160,000 miles) Runs great shifts great.

    I took it in to my local mechanic for an oil change and a general inspection. I do all my own work typically on my vehicles but wanted a true mechanic to look it over (I'm not a mechanic by trade) so I know everything is in good working order.

    They noted that the transmission fluid was dark (almost black) and recommenced a transmission fluid and filter change. (I've only had the truck since August and do not know previous maintenance on it) I know they're not trying to up sell me services as they are aware I do my own work. I'm hesitant as I've read horror stories about transmission fluid services on a high mileage transmission and the tranny going out after the service.

    Do I drop the pan and change filter and replace the fluid that came out, or do I also evacuate the rest of the fluid in the cooler/lines/torque converter (not a pressurized flush)? Or do I wait for the season to be over and then do the fluid/filter? I'd rather it blow up after winter.

    Thanks in advance.
    Sorry for long post.
  2. ratherbfishin

    ratherbfishin Senior Member
    Messages: 205

    Two schools of thought....some say a flush, especially on a truck with that amount of miles just stirs up the crap and pushes it into the valve body etc. that is my belief also. Some say the flush is good because it gets all the torque converter etc.
    I personally go for the pan drop with filter change. Do it, run the truck for a bit, do it again. After a couple changes, see what the fluid looks like. After that, you can simply suck out the fluid in the pan through the dip stick tube and just do the fluid.
  3. Boomer123

    Boomer123 Senior Member
    Messages: 371

    I have my trucks flushed every couple of years depending on usage. No issues with this.
  4. mpriester

    mpriester Senior Member
    Messages: 424

    I'd do a fluid transfer. Unhook the pressure line going into the cooler and run it into a container of some sort, start the truck and pump out 1 gallon, add 1 gallon new fluid, do this until the fluid is nice and red coming out and your done.
  5. johnhenry1933

    johnhenry1933 Senior Member
    Messages: 256

    What about the filter?
  6. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,403

    Have a shop do it. Flush machines aren't pressurized they use your transmission pump. By the time you buy all the fluid, mess a round with trying to do the whole two bucket method, spill crap everywhere etc you'd be better off just having it done.

    And most people don't change the filter anymore. Just flush it through
  7. GetMore

    GetMore Senior Member
    Messages: 179

    I cannot say with any certainty if it is safe to change the fluid, or if it will cause the transmission to explode. I've heard the same thing from a number of different mechanics.
    There is one person that said sometimes the new fluid starts picking up the debris that has settled in the transmission, and it is this debris that destroys it. His solution (if I remember it correctly) was to change the fluid (I don't know if it mattered what method was used) and then drive it for a week. He would then change some or all of the fluid again, drive another week, and then change the fluid yet again. I know I must be missing some critical parts of this. I think he would drop the pan and inspect for debris, and when no new debris was showing up he would call it good. I imagine that there must have been a filter change or two in there.
    It makes sense, though it also seems like a lot of work. However, if it works it is less work than changing a transmission.

    On the other hand, staying on top of fluid maintenance in the transmission is much simpler, so long as you get the truck soon enough. Can't do anything about previous history on a used truck.
  8. bmc1025

    bmc1025 Member
    Messages: 41

    Drop the pan and replace the filter. While the pan is off you can inspect the grime in the pan and filter to get a good idea of how the trans has been treated in the past. You are not going to cause a good transmission to go out because you changed the fluid.

    Sad thing is 200.00 in parts and a torque converter is all it takes to rebuild most failed 4l60 transmissions.
  9. Plowtoy

    Plowtoy Senior Member
    Messages: 929

    If your going to have it flushed, do that first to catch any debris in the "old" filter. Right after the flush, drop the pan (which requires taking the trans mount loose and jacking up on the t-case to get the clearance you need) and change the filter and fluid that comes out. The damage is already done, changing the fluid will not make it worse. The Tahoe in my sig was the same way when I bought it at 204000 miles. It now has 227000 miles on it and works like new. Change it out every year from here on out... Good luck