Well, I tackled this job today. Not going to lie, it was pretty frustrating, especially for a shadetree like me. I'll post my experience, hopefully it will help someone out. It took me about 4 and a half hours.
Breakdown of costs:
4 gallons ACDelco Dexron VI: $24x4 = $96
ATP gasket & filter set: $20
Cooling line adapter: $11
10' of 3/8" ID hosing: $5
Pick tool set from Harbor Freight: $3
Degreaser/shop towels for the pan: $7
Total: $142.
The dealer wanted $339 for this service.
The first snag I ran into was getting the c-clip off the "quick release" cooling line. If you think your pick tools are small enough, chances are, they aren't, you need a really freaking tiny pick tool to get that off there. I messed around with it for 15 minutes until I got the end of the pick around the clip. Having barely any room to mess around below the coolant line doesn't help either. There's probably a specialized tool for removing the clips but whatever, I don't do this often enough to buy it. Then when I was putting the adapter on, my fear came true, I dropped and lost the clip. Unless you put it on just right, it will pop out and go flying. I taped the hose in place so it wouldn't fall out while pumping fluid. Draining the fluid went well. Just as the tutorial says, it'll pump about 3.5-4 quarts out in about 30 seconds before it starts to bubble. My old fluid was dark brown. Once I got that out, I went underneath to get the pan out.
The pan bolts come off easy. They're 10mm. I was able to use the lever method that Meccanoble used (thanks for that one, man) to lower the exhaust, but it was nervewracking because you're forcing the exhaust to go where it doesn't want to go. Even with that it was a huge pain to get the pan off. It will get hung up on a component on the passenger side, then when you slide it forward, it will get caught on the cooler lines. There's a 15mm bolt holding the cooler lines in place that you can take off to get a tiny bit more movement, but since they're hard lines they don't move much. I had to twist the pan sideways just right to pull it out. It had about a half a quart in it. Worth noting that on a 6L80e you don't have to remove the shift linkage or even the heat shield!
The filter comes off easy, but the ring gasket above it is another story. It was jammed in the bore pretty good. I used wire-cutters to cut a notch in the side, and then another notch, and from there I was able to get a screwdriver in between the bore and the ring. Once you can bend it, it will come out no problem. The new one fit tight, but you can tap it in with a 7/8" socket on an extension and a hammer. I just kept tapping until it looked like it was touching the transmission. After that's in, the new filter should give you zero trouble going on.
Oh yeah, Simple Green worked wonders for cleaning the pan. The magnet was a pain to clean since all the tiny tiny shavings want to stick to it.
My old gasket looked good, but I decided to put the new one on anyway. When you do this be sure to clean the area underneath where the gasket was. Mine was a tiny bit misshapen so that the locator pins didn't want to stick directly up. This made it a huge pain in the ass to get it lined up. Get two of the bolts handy so you can put one on the front and one on the back as soon as you get the locators lined up. GM recommends tightening the bolts in a certain order. Is it important? Not sure, but I wasn't going to take the chance. I torqued them up in that order to 80 in-lb. and refilled the transmission. When I started the truck, the fluid was coming out really slowly, and in spurts, so I was freaking out thinking that I messed up the pump or something. But I shut it off, turned it back on, and it began flowing like normal again. I got about 3 more quarts out. Did that process twice more. Then the fourth time, I filled the transmission to the cold fill line. I had 16 quarts and used them all. Glad I left a full gallon for the final fill, because it took all of it.
It was about this point that I finally found that damn c-clip. It was on that flat plastic area right in front of the wheelwell retaining plastic. Maybe yours is there too if you drop it.
Here's where the fun starts, I took off the hose and reconnected the cooler line, started the truck, drove around the block, parked it and let it run. Before long I look underneath and see a nice pool of red. So, got back underneath, seems the leak was coming from the rear of the gasket, even though I am 100% certain that the locator is lined up and those bolts are torqued to spec. I decided it couldn't hurt to go above the spec just a tiny bit, so I grabbed my 3/8 ratchet and turned each bolt about a quarter turn. Not much at all. I just finished an hour ago and that seems to have stopped the dripping, but there's still moisture there even after I dried everything off. I don't know, maybe the new gasket needs to swell up? Hopefully it quits leaking but I'll be keeping an eye on it.
Anyway, my truck has 130k miles and unknown history on the transmission. It never shifted badly besides some hard shifts at WOT. Can't wait to take it out on the desert roads and see if that's improved. If anyone has any questions about the flush, feel free to ask. I'd be glad to help out. It's worth it for the peace of mind. If I can do it, you can too.
