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2007 gmc envoy_denali
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90 Posts
Don't flush the transmission ... service it correctly by dropping the pan and then you can see inside to get a decent appraisal of it.

Tear the old filter apart to see what it's caught and clean the magnet to see how much ferrous material it caught too.

Those things won't be done by flushing. You dont need to replace all the fluid every time ... besides, I would never allow my customers to risk crippling their vehicle by flushing.

I've had overhauls created by other shops that did flushing. It's just risky on an older unit.

PS ... the reason why I recommend the drill-and-screw pressure test is because not many people have the special socket to remove an oxygen sensor without damaging it.

PPS ... don't take any advice from AAMCO. That's like going to a witch doctor for orthopedic surgery. Belts, hoses and a wax job won't fix performance issues.
I couldn't disagree more on not flushing the transmission. I flush everything I own no matter the miles and have yet to kill one. Granted I don't do it to try and fix something, rather old, nasty, varnished fluid simply cannot perform as well as fresh fluid. I drop the pan, put a new filter in, and refill. Next I pop off the return line, shove a hose over it, and put that in a milk jug. Fire up the car and let the tranny do the pumping. Fill 3 gallon jugs and you're good and clean.

Also OP, was this thing ever not gutless? I'm wondering if when it's all 100% it won't be up to what you're expecting? They're not rocketships.
 

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2007 gmc envoy_denali
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If the trans is healthy absolutely flush it the way I described, it will buy you life in the long run. How big of a trailer do you want to tow? My sister had a 06ish 4.2 TB and I used it to tow Uhaul's biggest trailer from MI to CO. I kept it in 3rd gear the whole time and it was a champ the whole way, zero mods. The catalyst code may be a second order effect of the other stuff. If I were you, I'd swap #3's coil with another and see if the code stays or follows. If it follows, you know it's a junk coil.
 

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2007 gmc envoy_denali
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Good to know, ill give that a try... As it was I was thinking of replacing all the plugs and coils anyway cause no one replaces t hose until theyre bad... As for trailer size, we were wanting to get a 14x6 cargo to convert into a camper after the move and stuff... Nothing crazy
I just looked and it was a 6x12 tandem axle that I hauled my sister's crap out here in (in her own car).

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For the record, I made a single attempt to back that trailer to the house. Not that I'm bragging or anything. . .

I'd say a 14x6 won't give you any trouble. I've hauled bigger with out Envoy at altitude. Let us know how it goes.
 

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2007 gmc envoy_denali
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By all means ---- flush it!

That singular process bought me a 52 foot yacht in Dana Point.

View attachment 58812


Love it --- bad advice backed up by ONE anecdote.
Yes, because my single post pertains to a single vehicle let alone a single transmission type. Keep pushing 20 year old, nasty, broken down fluid on folks with otherwise healthy vehicles who'd actually benefit from a flush. Great way to make their vehicles last forever.
 

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2007 gmc envoy_denali
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Look, all I know is the transmission fluid is black and smells burnt... it needs to go period... As of right now, I cleared the codes and I will see what pops back up (if anything) in a couple days after driving it around and what not... Ill post again on saturday with what ever codes popped up and go from there
Regardless of your stance on the transmission fluid flush, cylinder 3 has something up so expect that to return.
 

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I am no fan of Ravalli's "make a joke of everything" attitude, to the point I hate reading his responses. But I do because once you get past his attempts at humor when most need advice, not jokes, his advice is 99.9% spot on.
Superchrged111 is the ONLY person on these forums who advocates a full trans. flush. The ONLY one.
Take that as you will.
I am on other forums where I'm not the only one advocating for full flushes on 4L60Es, there's nothing special about the ones they put into Trailblazers. Have fun being a hack if you think it's cool to keep 20 year old fluid in your transmission. Does that logic work for the engine? Brakes? Cooling system? Power steering system? Axles? Transfer case? Or does old, nasty fluid cause issues there too? Or do you just ignore it?
 

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2007 gmc envoy_denali
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90 Posts
O2 sockets suck! Last stubborn one I pulled I ended up cranking a set of these bad boys down on and whacking with a hammer after a couple of torch cycles to break it free. . . and I don't live in the rust belt!

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You snap them down, then cram a screwdriver back in the red screw and keep tightening them. They are le-git and THE reason I got that O2 out as opposed to saying to Hell with it and welding in a new bung with a new sensor elsewhere. YMMV.
 

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2007 gmc envoy_denali
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Please stop arguing over the flush guys, its not helpful here :(
I'm sorry GG, I just hate it when folks repeat bad info and try and scare you into neglecting your vehicle. There are a lot of folks with high mileage rigs who would benefit from a flush, but are too scared because of what's been going around since before the internet. My personal experience spans 4 full flushes, 2 of which were 4L60 rigs, and none of them died. Filter changes on my 1500 would NOT get the fluid clean. That's worth exactly what you paid for it. I have heard the machine is the one that tends to kill them as it has a rather high operating pressure, and I have heard if your transmission is acting funny and you try a flush as a hail Mary it's probably going to kill it, but if you have a healthy trans and flush the way I laid out with the transmission's internal pump by simply removing the return line, myself and others have had real world good experiences and nobody here can take that away. Once you're past that hurdle, you can continue to flush on schedule and get the longest possible life from your transmission. For the time being, this likely plugged cat and VVT issue should take precedence. Best of luck!
 

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2007 gmc envoy_denali
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So I officially know what the issue is thanks to removing the updraft O2 sensor... the cat is completely clogged so it will need to get replaced... as soon as I removed it, I was able to do 0-75 in about 12 seconds as to where before it would take 45-65 seconds... and as soon as the O2 sensor was put back in, it bogged down haaaaaaaaaard
So once that VVT code is all cleared up, any chance it's clean itself? Is there some sort of miracle juice you can pour into an almost empty tank to get it cleaned? Was the VVT stuff the cause of the clogged cat? Wouldn't want that problem coming back.
 

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2007 gmc envoy_denali
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90 Posts
Did you get this thing on the cheap? That's a lot of crap to have to run down on what I perceived to be a recent purchase. On the plus side, it's not a rotbox being an AZ rig, so worth sinking some coin into if it's going to stay around for a while.
 
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