Bbob, Purging/exchanging tranny fluid
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Northstar Engines and System Technical Discussion Discussion, Bbob, Purging/exchanging tranny fluid in Cadillac Engine Technical Discussion; My 2002 4.0 v8 Aurora has the 4T-80? tranny. Is the fluid exchange as easy as disconnecting the tranny cooling ...
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    Aurora5000's Avatar
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    Bbob, Purging/exchanging tranny fluid

    My 2002 4.0 v8 Aurora has the 4T-80? tranny. Is the fluid exchange as easy as disconnecting the tranny cooling line hose, letting the engine at idle pump out the old fluid while you put in 12 quarts on the top for a purge/exchange? If this is correct, it seems so simple to do.

    Thanks,
    Steve


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    Re: Bbob, Purging/exchanging tranny fluid

    Yea, you can do it that way.....but....I wouldn't just pour 12 quarts in on top of the dirty fluid and start it up. You just created 12 more quarts of dirty fluid that way.

    If you want to purge all the fluid this is the best way...... drop the bottom pan to clean the screens and inspect and clean the inside of the pan. With the bottom pan off you can drain the side cover with the hidden drain plug to get most of the old fluid out before doing the purge maneuver. Put the pan back on, fill it up with fresh fluid and open the cooler line. Start it up and idle until you see fresh fluid coming thru. You'll likely use more than 12 quarts, though. This way you will not mix your fresh fluid with all the old fluid stored in the side cover.

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    Re: Bbob, Purging/exchanging tranny fluid

    maybe its just me but i dont really see the benefit of flushing the trans, you still arent replaceing the filter and cleaning the crud out ot the bottom of the pan by doing that, unless you have already done that i would suggest doing it the old fashioned way and take a trans fluid bath and remaove the pan.

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    Re: Bbob, Purging/exchanging tranny fluid

    Quote Originally Posted by cart69
    maybe its just me but i dont really see the benefit of flushing the trans, you still arent replaceing the filter and cleaning the crud out ot the bottom of the pan by doing that, unless you have already done that i would suggest doing it the old fashioned way and take a trans fluid bath and remaove the pan.
    The problem is that dropping the pan only removes a surprisingly small amount of fluid. Removing the drain plug gets more out of the side case (like bbob said), but I've found that I've been able to get only about 8 quarts tops out by doing both. The rest needs pumped out of the torque converter and cooler. I haven't done it yet, but I may use the purge maneuver described above.

    Jim

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    Re: Bbob, Purging/exchanging tranny fluid

    sorry i should have gone a little further with my post, i dont see the benefit of flushing without change the filter as well, i know what you mean about the torque converter and all, my brain just was thinking of the burrito i was eating for lunch!! lol

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    Re: Bbob, Purging/exchanging tranny fluid

    Quote Originally Posted by cart69
    my brain just was thinking of the burrito i was eating for lunch!! lol
    MMMmmmmm, burritos... Transmission? What transmission?
    Mike

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    Re: Bbob, Purging/exchanging tranny fluid

    Side question Bob...

    1. Do I the drain off fluid hot or cold?

    2.When I drain bottom and side pans, how many quarts do I put back in before I do the purge maneuvar at idle?

    3. How many quarts aprox. should I buy to do this?

    4.After I have started the engine at idle, do I put in 1 quart at a time or more at this point?

    Thanks for all of your help.
    Steve

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    Re: Bbob, Purging/exchanging tranny fluid

    It is far easier to work with cold. Since you are dropping the pan to clean it there is no real reason to try and do it hot since you will be getting any particulates out of the pan that might settle when the fluid sits cold....

    I think it takes about 12 quarts to refill it after draining the lower pan and side cover with the hidden bolt drainplug for the side cover. I would put the 12 in and start it up if you are going to purge thru the cooler line after dropping the pan.

    Start the engine, idle it and start pouring. It will go fast if you want to keep up....LOL....I would just put the 12 quarts in , start it up and idle it and watch the fluid going into the bucket thru a piece of clear tubing. When it is nice and red indicating new fluid, shut it off, connect the cooler line and refill about what went into the bucket....start the engine back up, idle, cycle the trans thru the gears and check the level with the dipstick and start from there filling to the correct level. It sounds like a good idea to pour as fast as the trans is pumping it out but it is hard to do and likely will make a mess. It will not hurt the trans at all if it "sucks air" for a moment idling and you will likely quit before you pump all 12 quarts thru....have a big bucket....so just refilling and starting it up until fresh fluid comes thru is fine. forget about trying to pour and watch and run the engine at the same time.

    Hard to say how long you are going to purge and how much fluid will go thru into the bucket. You shouldn't have more than 4 quarts left in the whole trans after a bottom pan and side cover drain so theoretically you should see nice red fluid after 4 quarts from the torque converter has run into the bucket...but it will probably take more. I would get about 20 quarts total I think.....just my estimate to have enough to be able to finish the job.

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    Re: Bbob, Purging/exchanging tranny fluid

    Will do. All of us on the boards appreciate your help.

    Thank you kindly,
    Steve

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    Re: Bbob, Purging/exchanging tranny fluid

    Did fluid exchange this weekend. Worked just fine. After draining of old fluid, I put in topside 8 quarts to start out with. Ran 30 seconds and put in another 6 quarts. Was seeing nice clean red fluid. Put line back on and topped off with another 2 quarts. As you said in the 16 qt. neighborhood.
    As a side note, that same day I got a reminder notice from dealership to bring in car for a tranny flush-fill. $149.
    Thanks,
    Steve


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    Re: Bbob, Purging/exchanging tranny fluid

    I need to do this - my fluid is still frothy from the water. Ironically, it runs and shifts fine. I've put about 20 miles on the car (I'd put more, but I can only drive around my neighborhood because I don't have legit license plates). Stop-n-go, hard accelleration (love the sound of the V8), light throttle, reverse - works fine under all conditions.

    Does the trans get hot enough inside to "boil" off moisture? Just curious.

    Anyhow, back on the topic at hand: Which cooler line do I unhook? Top one is easy to get at, bottom not so much. I guess the real question is which line is the "in" line (fluid going into the cooler) and which is the "out" line?

    TIA,
    Jim

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    Re: Bbob, Purging/exchanging tranny fluid

    Quote Originally Posted by turbojimmy
    I need to do this - my fluid is still frothy from the water. Ironically, it runs and shifts fine. I've put about 20 miles on the car (I'd put more, but I can only drive around my neighborhood because I don't have legit license plates). Stop-n-go, hard accelleration (love the sound of the V8), light throttle, reverse - works fine under all conditions.

    Does the trans get hot enough inside to "boil" off moisture? Just curious.

    Anyhow, back on the topic at hand: Which cooler line do I unhook? Top one is easy to get at, bottom not so much. I guess the real question is which line is the "in" line (fluid going into the cooler) and which is the "out" line?

    TIA,
    Jim
    Trans fluid will stabilize at or near the engine coolant temperature. Some water vaporization will occur at 190 to 200 degrees. The top of the rubber vent line might give you a clue to what is vaporizing in your transmission.

    My '98 and '04 both return to the transmission from the top line (out) in the cooler. You will find a quick disconnect fitting with a small clip and an even smaller O ring. I fabricated a brass pipe thread fitting to adapt the cooler plumbing to something I could clamp a flex hose to. I have a pix somewhere if you need a look at the adapter I used.

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    Re: Bbob, Purging/exchanging tranny fluid

    Quote Originally Posted by JimD
    I have a pix somewhere if you need a look at the adapter I used.
    That would help if you don't mind digging it up. Otherwise it would just puke it out the top of the cooler all over everything. Unless I can get at the bottom fitting somehow.

    Also, once the water and fluid mix to make this pink milkshake, how long do you think it would take to separate again? Is my best bet to drive it around to make sure it's mixed well before purging? Or let the water settle to the bottom and then drain it? The first time I drained it I got water, then oil. Subsequent drains (4 of them) were just trans-fluid looking-stuff (but a little weaker consistency than true Dexron/Mercon).

    Thanks!

    Jim

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    Re: Bbob, Purging/exchanging tranny fluid

    Not sure about the moisture that might remain. If you could get it heat soaked on the highway, that would help. Maybe doing the purge several times and getting it hot between purges??

    The adapter I used screws into the cooler tank in place of the quick disconnect fitting. Much faster than pulling the pan and enjoying a fluid bath.

    I pump the system with the engine at idle and shut off the engine as soon as fluid stops flowing. Takes a little more than 11 quarts to refill.

    Good luck.....

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    Re: Bbob, Purging/exchanging tranny fluid

    JimD - thanks for the info. Is that 5/8" pipe thread?

    I'm going to drop the pan anyway. As it sits, the water makes its way to the pan and the bottom of the side case resevoir. I'm going to drain it, fill it, then let it pump out as I dump fresh oil in the fill hole (as bbob described - I think).

    Thanks again,
    Jim

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