GM 4L80E Filter Replacement - In Middle of Job

[Caman96]

Which of the two (2) cooler lines? So the engine at idle will flow fluid through the TC? Is it possibly damaging to the trans to have the fluid run through the cooling line OUT of the system until its empty? I do have two gallons of Dextron. I may need three, actually. Yes? I'm just worried about destroying the second most expensive (and arguably most complex) component on this amazing truck. I'm not worried at all about the "old wives tales" (rumors) that new fluid will ruin an old trans. Just concerned about this process. Thanks guys, I REALLY appreciate it. P

This is the most non-invasive way to transfuse the fluid. It’s just doing what your transmission normally does. It’s never been that “new” fluid is bad, but the process these Lube shops use with their system that applies different pressures to transmission that may or may not agitate it. All’s I know is my transmission has brand new fluid. And that’s a good thing.

 

[Pinger]

Which of the two (2) cooler lines? So the engine at idle will flow fluid through the TC? Is it possibly damaging to the trans to have the fluid run through the cooling line OUT of the system until its empty? I do have two gallons of Dextron. I may need three, actually. Yes? I'm just worried about destroying the second most expensive (and arguably most complex) component on this amazing truck. I'm not worried at all about the "old wives tales" (rumors) that new fluid will ruin an old trans. Just concerned about this process. Thanks guys, I REALLY appreciate it. P

It won't matter which line - the return would be better as you'll also purge the cooler. If you end up removing the lower one it will gravity drain anyway.

There's no danger. Just shut the engine down when the fluid flow stops or, before if you see clean fluid coming through. If the fluid coming through was still dirty when it stopped flowing, add more fresh oil and repeat the process. It will be less stressful if you have a helper to take control of the ignition key.

Check the quantities quoted for your trans. The figures for the 4L-80E in the GM manual are slightly higher than actually needed. From memory it is around 12-14 litres and it's very roughly split half and half between gearbox and TC. Subtracting the service refill figure from the overhaul figure will give you an idea as to how much to expect from the TC.
There is still a very small amount left within the gearbox but I finally accepted Schurkey's view that it isn't worth worrying about. The bulk of the oil resides in the pan and TC and with that changed for fresh that's a maximum result for only slight more than minimum effort.

 

[454cid]

You're saying a person DOES NOT have to worry about pumping out all the ATF with the truck idling? I would have thought it would be like power steering where you don't want the pump to run dry.

 

[Caman96]

I had my son in truck, as soon as you see a flow change or bubble, ignition off then add more fluid. I was a little nervous about it at first, but it’s pretty straight forward.

 

[0xDEADBEEF]

Consider a mightyvac. I stick it down on the dipstick tube and suck out 1 gallon and then replace. Drive it a couple a weeks and repeat until fluid looks good. It's not the most efficient or cost-effective procedure, but it's super simple, low-risk, and you don't get dirty.

 

[454cid]

Consider a mightyvac. I stick it down on the dipstick tube and suck out 1 gallon and then replace. Drive it a couple a weeks and repeat until fluid looks good. It's not the most efficient or cost-effective procedure, but it's super simple, low-risk, and you don't get dirty.

OP has a 4L80E, which should have a drain plug in the pan.

 

[0xDEADBEEF]

OP has a 4L80E, which should have a drain plug in the pan.

I'd still use my mightyvac because I don't have get under it and it's a much quicker and cleaner process.

 

[stutaeng]

OP has a 4L80E, which should have a drain plug in the pan.

Not all of them had the drain plug (first photo from an 06 SUV), but his clearly has it ... I've add my own drain plugs to stock pans that didn't have it: Just a 3/4" bolt with a nut welded on the inside and a nylon washer as sealing ring. Works well (third photo.)

On the issue with the stripping the plug bolt, that seems common. I suppose you can weld a 3/4" nut on the end to make it less likely to round off? It will just protrude slightly below the pan? I had to do that one of one of my trucks (different truck), but with a welding rod, under the truck on dead grass in my back yard. Not fun! That was last option after everything failed to remove bolt and I was pissed. (second photo) Out of the truck you can probably do a nicer weld than me. LOL.

 

[454cid]

I'd still use my mightyvac because I don't have get under it and it's a much quicker and cleaner process.

I'm not sure what you have. To me a MityVac is a hand held vacuum pump for bleeding brakes. I can't imagine that being convenient for pulling out a gallon of ATF, so I guess you've got something bigger/more-expensive?

 

[0xDEADBEEF]

I'm not sure what you have. To me a MityVac is a hand held vacuum pump for bleeding brakes. I can't imagine that being convenient for pulling out a gallon of ATF, so I guess you've got something bigger/more-expensive?

I may be calling it the wrong thing. It's large and not handheld. It kind of looks like a bicycle pump with a large reservoir. It can push or pull fluid.

One of my favorite tools.

Found it:

links isn't working ...

Mityvac 7201​