Tranmission Fluid Replacement

[NEECAPR]

I've used the SNOWDRIFTER method for the past ~160k miles on our 1999 Yukon SLE. I do it [almost!] every engine oil change because I fear a step change in oil chemistry and I only get about 1 3/4 qts each time. Used Dexrons, now Dexron VI.
The car has 209k miles on it now and with that, the modulation and upshifts are as good and smooth as I'd ever ask for. Oil on dipstick has always been a nice clear red.

 

[Courtney D Taylor]

Hey All,

I bought my 2001 Yukon originally at 108k miles back in 2010. I currently only have 140k on it, as the first half of ownership was finishing college and grad school and I haven't had to drive much since then either. I started doing my own work on my vehicles in the past 3 years using the Yukon to learn on, and I've come to realize that I have no idea if the transmission fluid was changed out at 100k from the previous owner. I really don't know anything about the maintenance that he did (I bought the truck on Craiglist private party).

From looking on this forum and on some others, I have seen the recommendation NOT to change the transmission fluid if you are way past 100k miles and haven't had any problems. I don't fully understand why, though I think I read something about different seals.

The transmission fluid is definitely brown, though not as brown as I would think it would be having gone through 19 years and 140k miles if it wasn't changed at 100k.

So my question is, do I go ahead and change it under the assumption that it wasn't changed at 100k? Or is there some risk to changing it now that it is so far past the time and I should just ride it out?

I've read of dropping the pan and replacing the filter, not flushing, so that's what I was thinking of doing.

Any help is appreciated.

I was recently going through the same issue and my friend that is a mechanic said that changing that far past is at higher risk of causing problems especially if you aren't having any issues.

 

[OR VietVet]

I was told by trans shop guys that doing a flush of the trans system when it has not been done in a very long time and after lots of miles will be a shock to the clutch plates and damage them and therefore come apart and slip badly. The filter and fluid change should be ok because you have new fluid mixing with older fluid and is not such a shock to the system.

 

[calsdad]

I just flushed the fluid on the 6L90 in my 2010 Yukon XL 2500 a few weeks ago.

First I sucked all the fluid out of the pan using one of those Mityvac tall cylinder type fluid excavators. Then I dropped the pan - installed a deep pan - and a new filter.

Filled the pan up again until I had fluid on the dipstick.

Then I disconnected the top trans cooling line from the radiator - installed a trans cooler adapter fitting (picked up from RockAuto) into the top port on the radiator - and ran a rubber hose ( think it was a 3/8") from the cooler fitting down to the Mityvac. I discovered that the rubber hose neatly plugged onto the port at the top of the Mityvac so I could just flush directly into the Mityvac reservoir.

That made it easy - I could just turn the truck on and run it while watching the Mityvac reservoir fill up - and it made it easy to monitor the amount of fluid I had just flushed out - which made it easier to make sure I didn't draw the pan down too far and expose the filter.

The fluid when I first started flushing was a deep red , by the time I finished the fluid was coming out nice and bright red and clean.

Took it for a drive afterwards - and the shifting was obviously better.

My truck has about 105,000 miles on it. Been driving it for a few weeks now and I haven't noticed any adverse effects.

 

[rockola1971]

I would never flush a tranny. Drop the pan and filter and put new fluid in ok. Never ever run a transmission over a 1/2 qt low on fluid. After a fluid change make sure you know exactly how much you removed and install that much back in BEFORE you even think about sticking that key in the ignition and turning forward. The most common tranny failure that is self induced after a tranny fluid change out is caused by running the transmission low on fluid. That tranny has components spinning while the vehicle is sitting there in park idling.

 

[01YukonSC]

Figured I would post a follow-up to this after I completed it to help whoever may read this in the future.

I did just the pan drop, filter change, and refill since I'm basically at 150,000 miles and don't know if the fluid was changed at 100k.

First, removing the exhaust/catalytic converter to be able to remove the drain pan was terrible. There is another method to remove the shifter cable (?? On the passenger side) using a T-40 bit. But the bolts were seized up and I couldn't remove them that way. That would probably be the easiest way to go in the future.

Also, for fluid, I ended up using 5.75 qts to refill. Bought 5 initially and had to go back and get another.

 

[Rocket Man]

Figured I would post a follow-up to this after I completed it to help whoever may read this in the future.

I did just the pan drop, filter change, and refill since I'm basically at 150,000 miles and don't know if the fluid was changed at 100k.

First, removing the exhaust/catalytic converter to be able to remove the drain pan was terrible. There is another method to remove the shifter cable (?? On the passenger side) using a T-40 bit. But the bolts were seized up and I couldn't remove them that way. That would probably be the easiest way to go in the future.

Also, for fluid, I ended up using 5.75 qts to refill. Bought 5 initially and had to go back and get another.

I have always put a prybar on that shifter cable bracket and pried just a bit, it’s enough to wiggle the pan out without trying to get to that horrible bolt. If it bends you can bend it back after the pan is back on.

 

[SnowDrifter]

Figured I would post a follow-up to this after I completed it to help whoever may read this in the future.

I did just the pan drop, filter change, and refill since I'm basically at 150,000 miles and don't know if the fluid was changed at 100k.

First, removing the exhaust/catalytic converter to be able to remove the drain pan was terrible. There is another method to remove the shifter cable (?? On the passenger side) using a T-40 bit. But the bolts were seized up and I couldn't remove them that way. That would probably be the easiest way to go in the future.

Also, for fluid, I ended up using 5.75 qts to refill. Bought 5 initially and had to go back and get another.

Bracket comes off from the top with some t30 or t27 (I think?) somewhere around there. It's blind but you can get it w/ a stubby 1/4" ratchet. Was going to try to find a good pic, but TBH just feel it. 2 bolts

Pop the cable off - just presses in. Position a set of pliers and use that to squeeze it off.

 

[MaBs413]

I just flushed the fluid on the 6L90 in my 2010 Yukon XL 2500 a few weeks ago.

First I sucked all the fluid out of the pan using one of those Mityvac tall cylinder type fluid excavators. Then I dropped the pan - installed a deep pan - and a new filter.

Filled the pan up again until I had fluid on the dipstick.

Then I disconnected the top trans cooling line from the radiator - installed a trans cooler adapter fitting (picked up from RockAuto) into the top port on the radiator - and ran a rubber hose ( think it was a 3/8") from the cooler fitting down to the Mityvac. I discovered that the rubber hose neatly plugged onto the port at the top of the Mityvac so I could just flush directly into the Mityvac reservoir.

That made it easy - I could just turn the truck on and run it while watching the Mityvac reservoir fill up - and it made it easy to monitor the amount of fluid I had just flushed out - which made it easier to make sure I didn't draw the pan down too far and expose the filter.

The fluid when I first started flushing was a deep red , by the time I finished the fluid was coming out nice and bright red and clean.

Took it for a drive afterwards - and the shifting was obviously better.

My truck has about 105,000 miles on it. Been driving it for a few weeks now and I haven't noticed any adverse effects.

 

[MaBs413]

What brand deep pan did you install?..