INPUT ON TRANS PAN DROP, FILTER, GASKET & FLUID CHANGE

[denalilex]

input on trans pan drop - complete fluid flush - filter, gasket & fluid change on high mileage vehicles ? (GMC YUKON DENALI 6.2L v8, 6L80)

when i was checking my fluids yesterday - trans looked a little high… siphoned some out & it was like black tar. i know sometimes it’s advised against to change these components on a high mileage vehicle. but i cannot in good faith put that fluid back in my truck. & so i’m stumped.

is this a legitimate concern with older GMs - or should i be good to drop the pan, clean it up & fill it up new?


i’ve purchased ACDELCO filter, filter seal & cork gasket kit as well as 3 gallons of ACDELCO dexron vi ATF for the task but would feel better with some input from some more seasoned of the members on here.


tia
*sorry if this was addressed before & i missed it*

 

[gooffeyguy]

Mileage?

Personally, I prefer clean fluid and would change it. You probably won't need the cork gasket though, the OE rubber gasket is usually reusable unless it's torn or currently leaking.

Oh and 3 gallons of fluid would just be enough to flush it all out, but you may need an extra quart or two to top it off to the correct level when done

 

[donjetman]

Do a full flush. 6L80e holds about 3 gals. Disconnect upper atf line on the radiator. Start it up, pump 1 gal out, shut it off, replenish the 1 gal with new Dexron VI thru the dip stick tube. Repeat 2 more times.

When you only drop the pan, you only get 6 qts out.

 

[denalilex]

Mileage?

Personally, I prefer clean fluid and would change it. You probably won't need the cork gasket though, the OE rubber gasket is usually reusable unless it's torn or currently leaking.

Oh and 3 gallons of fluid would just be enough to flush it all out, but you may need an extra quart or two to top it off to the correct level when done

hey - sorry for the late reply. had a few personal issues to take care of & trucks been on the back burner. have been driving my pickup that i use for work & i’ve got no more patience for ford so i’m back to my yuk.

in the past few weeks - i’ve managed to completely psyche myself out as a result of reading other’s threads.


my trucks got 290xxx on the dash … less than 50k of them are mine.. PO was - afaik - a corporate entity… i believe a rental or limousine service .. along those lines. so i believe, or presume, that it’d been serviced - at least to some degree - over the span of its years.

the fluid is BLACK. as for burnt….i don’t really recall what burnt tranny fluid smells like but from what i’m gathering - it’s one of those “you’ll know it if it is” type things. it has no sour/stale/rancid smell to it. & no particles floating around.

i siphoned what i could from the dipstick. i was able to remove about 6 quarts. if you hold the tubing up to the sunlight while pumping - you can still see the red hue to it. if that matters.

rough shift 2-3 but i think that’s a software tech2 calibration update issue. i have to get my hands on a tech2 but idk anyone with one rn. my truck has updates available via GM’s vin lookup tool. a few for my TCM. so i don’t think that is a trans issue hardware wise. 2-3 feels like you broke your neck but all other gears are smooth as butter.

i bought the sonnax pressure switch rebuild kit for the 6L80… so i have new seals. i’m throwing the 4 codes that - on the 6L80 - have typically signaled seal failure on the pressure switches.


with all that novel length information - i hope i’ve covered it all. sorry i’m really bad at cliffnoting my point.

with all that said - would you recommend/suggest a full flush? i would do so via the cooler line radiator outlet & hose barb + clear tubing. or could this fry the trans? i would think it’s still in good shape. the 6L80 just has some issues unrelated to just the fluid i think.

i also have lucas trans stabilizer.

or just stick with the fluid i’ve already taken out & continue with the new filter & gasket i have, the switch rebuild & top off the 6 quarts of fluid ?


sorry again this is so long ugh. thanks for your reply

 

[denalilex]

Do a full flush. 6L80e holds about 3 gals. Disconnect upper atf line on the radiator. Start it up, pump 1 gal out, shut it off, replenish the 1 gal with new Dexron VI thru the dip stick tube. Repeat 2 more times.

When you only drop the pan, you only get 6 qts out.

hahah!! i just typed this all out in a reply to the other comment on here. literally asking what you wrote here. haha. i’m gonna paste it here & just get a confirmation from you if you don’t mind. i just wanna give all the details in hopes of not speeding up the death of my trans lol… which, btw, i know that anything i do to my truck is 100000% my choosing & my own risk. & any advice is so appreciated…

Mileage?

Personally, I prefer clean fluid and would change it. You probably won't need the cork gasket though, the OE rubber gasket is usually reusable unless it's torn or currently leaking.

Oh and 3 gallons of fluid would just be enough to flush it all out, but you may need an extra quart or two to top it off to the correct level when done

hey - sorry for the late reply. had a few personal issues to take care of & trucks been on the back burner. have been driving my pickup that i use for work & i’ve got no more patience for ford so i’m back to my yuk.

in the past few weeks - i’ve managed to completely psyche myself out as a result of reading other’s threads.


my trucks got 290xxx on the dash … less than 50k of them are mine.. PO was - afaik - a corporate entity… i believe a rental or limousine service .. along those lines. so i believe, or presume, that it’d been serviced - at least to some degree - over the span of its years.

the fluid is BLACK. as for burnt….i don’t really recall what burnt tranny fluid smells like but from what i’m gathering - it’s one of those “you’ll know it if it is” type things. it has no sour/stale/rancid smell to it. & no particles floating around.

i siphoned what i could from the dipstick. i was able to remove about 6 quarts. if you hold the tubing up to the sunlight while pumping - you can still see the red hue to it. if that matters.

rough shift 2-3 but i think that’s a software tech2 calibration update issue. i have to get my hands on a tech2 but idk anyone with one rn. my truck has updates available via GM’s vin lookup tool. a few for my TCM. so i don’t think that is a trans issue hardware wise. 2-3 feels like you broke your neck but all other gears are smooth as butter.

i bought the sonnax pressure switch rebuild kit for the 6L80… so i have new seals. i’m throwing the 4 codes that - on the 6L80 - have typically signaled seal failure on the pressure switches.


with all that novel length information - i hope i’ve covered it all. sorry i’m really bad at cliffnoting my point.

with all that said - would you recommend/suggest a full flush? i would do so via the cooler line radiator outlet & hose barb + clear tubing.

i also have lucas trans stabilizer.

or just stick with the fluid i’ve already taken out & continue with the new filter & gasket i have, the switch rebuild & top off the 6 quarts of fluid ?


sorry again this is so long ugh. thanks for your reply

 

[Geotrash]

hahah!! i just typed this all out in a reply to the other comment on here. literally asking what you wrote here. haha. i’m gonna paste it here & just get a confirmation from you if you don’t mind. i just wanna give all the details in hopes of not speeding up the death of my trans lol… which, btw, i know that anything i do to my truck is 100000% my choosing & my own risk. & any advice is so appreciated…



hey - sorry for the late reply. had a few personal issues to take care of & trucks been on the back burner. have been driving my pickup that i use for work & i’ve got no more patience for ford so i’m back to my yuk.

in the past few weeks - i’ve managed to completely psyche myself out as a result of reading other’s threads.


my trucks got 290xxx on the dash … less than 50k of them are mine.. PO was - afaik - a corporate entity… i believe a rental or limousine service .. along those lines. so i believe, or presume, that it’d been serviced - at least to some degree - over the span of its years.

the fluid is BLACK. as for burnt….i don’t really recall what burnt tranny fluid smells like but from what i’m gathering - it’s one of those “you’ll know it if it is” type things. it has no sour/stale/rancid smell to it. & no particles floating around.

i siphoned what i could from the dipstick. i was able to remove about 6 quarts. if you hold the tubing up to the sunlight while pumping - you can still see the red hue to it. if that matters.

rough shift 2-3 but i think that’s a software tech2 calibration update issue. i have to get my hands on a tech2 but idk anyone with one rn. my truck has updates available via GM’s vin lookup tool. a few for my TCM. so i don’t think that is a trans issue hardware wise. 2-3 feels like you broke your neck but all other gears are smooth as butter.

i bought the sonnax pressure switch rebuild kit for the 6L80… so i have new seals. i’m throwing the 4 codes that - on the 6L80 - have typically signaled seal failure on the pressure switches.


with all that novel length information - i hope i’ve covered it all. sorry i’m really bad at cliffnoting my point.

with all that said - would you recommend/suggest a full flush? i would do so via the cooler line radiator outlet & hose barb + clear tubing.

i also have lucas trans stabilizer.

or just stick with the fluid i’ve already taken out & continue with the new filter & gasket i have, the switch rebuild & top off the 6 quarts of fluid ?


sorry again this is so long ugh. thanks for your reply

The codes and the rough 2-3 shift tell me that the valve body has to come out to have the new check balls and other bits replaced on the bench with your kit. At that point, you'll be replacing the fluid anyway. In my opinion, new fluid alone isn't going to resolve the shifting problem you're having.

 

[robgreg75]

The first time I did the pan drop I installed a drain plug in it. The exhaust is in the way but if you have a light jack you can jack the exhaust down from the body and give just enough room to get the filter out.

 

[denalilex]

The codes and the rough 2-3 shift tell me that the valve body has to come out to have the new check balls and other bits replaced on the bench with your kit. At that point, you'll be replacing the fluid anyway. In my opinion, new fluid alone isn't going to resolve the shifting problem you're having.

right - yes i agree. the new fluid is not / was never an attempt to fix my shift issues….the fluid change came about due to my checking all of my fluids & noticing just how DIRTY it is & i couldn’t in good faith drive my truck with THAT pumping through the trans & so it’s been parked while i got around to finally doing it. but over the last few weeks, i’ve been seeing very differing views on flushing / just pan drop & refill with new the 6 quarts you remove. but that brings me to the point of - i cannot drive this truck with that fluid running thru it & even changing 1/3 of the fluid still leaves me with 66.6% horrificly dirty fluid & that’s not a good percentage imo.

but ok thank you for this advice - the check balls weren’t something i thought of…. tbh, this is my first time working on a vehicle in this capacity … like actually getting into the mechanics of it. & not just your average oil change, brake pads, etc. i’ve fixed, repaired & cleared 52 of 56 codes since getting it. so i think i’m doing ok lol.

i have to pull the valve body to get to the tehcm / pressure switches anyway so i’m trying to address everything that’s needing it while i have it apart & on my bench.

the way i’m looking at it is - i have nothing to lose. this truck lived well beyond its expected service years & that makes me happy. anything that goes wrong i can learn from.

so any & all advice is more appreciated than i can say … yous are far more seasoned & experienced than me. & this site is cool as you’re all working with the same trucks as me.

 

[denalilex]

The first time I did the pan drop I installed a drain plug in it. The exhaust is in the way but if you have a light jack you can jack the exhaust down from the body and give just enough room to get the filter out.

this is my plan! haha. it makes much more sense.

 

[swathdiver]

@skpyle