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Transmission Fluid?

Discussion in 'Trucks and Trailers' started by ron mexico75, Jul 9, 2010.

  1. ron mexico75

    ron mexico75 LawnSite Silver Member
    Messages: 2,015

    Wondering if some of you can help me out. I am about 500 miles away from hitting 100,000 miles on my 2002 2500HD Silverado with a 6.0 gas engine. As part of the 100K tune up would you even mess with the trans fluid?

    I mean, would you drain and add new fluid, flush and add new fluid or just leave it alone. I ask because you always hear horror stories about transmissions that are flushed and then problems start.

    This truck has been GREAT to me. Not one issue at of the ordinary in 7 years. I don't want to create a problem. So I ask, what would you do?
  2. ancjr

    ancjr LawnSite Member
    from Indiana
    Messages: 173

    I've often wondered this myself. I've changed the trans fluid and filter before in vehicles where the fluid was starting to get brown & oxidized. Cleaned out the pans as well, but never bothered with draining the converter too. Don't really know if I helped or hurt them, but I've never had any trans problems.
  3. ron mexico75

    ron mexico75 LawnSite Silver Member
    Messages: 2,015

    Yeah, I think I'm leaning toward just draining and refilling especially with 100k on the truck. Seems like on older transmissions when you flush them out you clear out gunk or debris that is actually helping in some way if that makes sense. At least I have heard numerous people say that.
  4. rlitman

    rlitman LawnSite Bronze Member
    Messages: 1,744

    Its somewhat of a toss up.

    Depending on the service schedule, you may have been due for several transmission flushes already.
    I've heard a number of stories just as you described, but in general, those transmissions were likely to fail pretty soon anyway, and probably because of lack of maintenance.
    If you're experiencing transmission issues already, or if your transmission fluid smells burnt, then a flush can loosen up sludge, and hasten its failure.

    Transmission fluid isn't bad when it loses its red color (the dye fades before the fluid goes bad), but the additive package (corrosion and wear inhibitors) do get depleted eventually. On the bright side, its not subjected to the dirty environment that engine oil sees, but the filter will pick up crap over enough time.

    So, if everything seems ok, it may be a good time to change the transmission fluid, before things go bad.

    BTW, Chevy's REQUIRE a special type of ATF (it should be in your manual, and is probably ATF+4), and using the wrong type (or just a generic ATF not specifically for Chevy transmissions), can be disastrous.
  5. whole9er

    whole9er LawnSite Member
    Messages: 74

    Im taking care of mine this weekend, this spring I bought a 04 2500hd with 52k Im closer to 58 now, my mechanic who im close friends with told me not to buy something with miles closer to the 100 mark for this issue. From my understanding the new fluid runs thinner and cleaner and acts differently on the valves and seals than the old fluid which makes the tranny gum up aka what your worried about. if you've cared for it I would probally do it but its a toss up, see what others say I have no real knowledge of this other than what my mechanic has told me. Just my 2 cents from what i've heard
  6. 360ci

    360ci LawnSite Senior Member
    Messages: 998

    I do as much work as I can on my vehicles. I change the fluid on my Dodge every two years, irregardless of miles, even if I put on 20K, I change the fluid. From empty, including a dry torque converter the system holds about 15 quarts. Replacing only 4 (standard trans fluid/filter change) still leaves 10 or so quarts in the system. So after 60K on the ODO it's best to change it every 2-3 years, especially when towing or hauling moderate to heavy loads.

    Now, if you had done a transmission flush at 60K, I'd advise to keep doing it every 40K thereafter, and not having to just change the trans fluid and filter every 25-30K. By flushing fluid early, you'll have a better chance of not having a problem. It's more prominent on earlier Dodge transmissions, where a transmission flush can dislodge larger gunk that has built up in the transmission, and can clog up the valve body starving the transmission of proper cooling and thus it overheats and you need to spend $2500 on a rebuild. Not fun. Not saying that that won't happen, but it's better to be overly cautious than going to long between services.

    Again, if you haven't had the fluid changed, spend the $90 or so and get out what fluid can be changed, and fill it with fresh fluid and replace the transmission fluid filter. It's better piece of mind down the road. Heat is what kills transmission fluid. A transmission flush, besides potentially clogging up the valve body can also move chunks of gunk into transmission cooling lines and can cause a failure when you least expect it.

    For about $50, and some mechanical knowledge, you can drop the transmission pan, drill a hole and thread in a temp sensor and install a gauge in the cab to keep an eye on fluid temperature. If you're OK with changing the fluid yourself, you can save money there as well, AND you can check the bottom of the pan and wash it off even if it looks clean.
  7. 360ci

    360ci LawnSite Senior Member
    Messages: 998

    I'll add that you should run synthetic fluid. Most manufacturers have their own fluid such as Mercon (Ford), Mopar ATF+4 (Dodge) and GM (Dextron?). Transmission fluid made in the last eight or so years is almost all synthetic based. Read the label if you want to change brands before you decide. Otherwise, stick with what the manufacturer recommends. For GM and Ford, Amsoil ATF and Mobil1 ATF are a good option if you want lower cost fluids with similar, if not better performance.

    Some fluids are thinner than others in terms of viscosity, but again, everything is stated on the bottle
  8. ron mexico75

    ron mexico75 LawnSite Silver Member
    Messages: 2,015

    Well, thanks for the recommendations. It has never been flushed or changed. So, I'll just go for draining and replacing and forget the flush. No issues with it, but I figure 8 years old with 100k miles it has to be due for fresh fluid.
  9. 360ci

    360ci LawnSite Senior Member
    Messages: 998

    You got that right!
  10. Bigred350

    Bigred350 LawnSite Senior Member
    Messages: 810

    I always drop the pan and put a new filter on then fill it back with fluid.\

    I have a 02 2500hd and its not to hard. Takes about a hour.

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