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03 trailblazer transmission filter, drop pan vs flush

So 40k ago I did my hillbilly transmission flush, disconnect the line at the radiator, got 12 quarts of fluid, kept pouring new in until the old dumping out looked cherry red. Now we made a 1k mile road trip, universal joint is good, but trans seems a little slower on shifting and would occasionally make a subtle clunk when kicking in the cruise control.
So I am thinking new trans fllter might do the trick.
So I took it to my regular guys and said I need a trans fluid change and filter. Service guy is Oh you mean a flush, and I say no drop the pan swap the 6 out of 12 quarts and change the filter, after 190k I think it needs it.
He is like ok we will do that.
My question is will a flush clean the filter? Is this the right choice? 190k miles, no trans filter change since I got it 100k and 10 years ago.

A flush will not clean the filter.

The only way to clean the filter is drop the pan and replace it which would have been my choice instead of did the hillbilly flush. At least assembly crud that had been removed by the filter would be gone. It is still there although the fluid was replaced. And a bit more than half will be replaced again with the filter change.

A pan drop only allows about a 1/3 of the transmission fluid to be replaced.

The rest is held in the torque converter, valve body, and the cooling lines.

I’d replace the filter and then have the fluid flushed.


I will look into the cost, though the drop the pan and do the filter they said 6 quarts, and the fluid is looking good, still thinking, thanks for the input.

Don’t know about access to your pan on the Trailblazer, but I have done 3 different cars. It is a fairly easy DIY job, but messy.

And tedious, with all those little bolts (20 each on my cars).
After I did my first messy one, I bought a huge water heater aluminum pan (I installed a removable cap on the drain) at a major builder’s supply store.

For in-between service I use my Liqui-Vac to suck the fluid out through the dipstick tube. I can change about 7 quarts, more than half, with zero mess.

The first time I remove a new to me pan, I install a petcock. Then I’ll be more inclined to do frequent changes because it’s so much easier to do. I’ll drop the pan maybe every 5 fluid changes just to see what’s going on but can count on one finger in 40+ years how many times I found something surprising in the pan if you do frequent changes…your vacuum provides a similar function

The TB has two different pan styles, shallow and deep. Make sure if you do it yourself, you buy the right filter. Easy to tell, the deep one has a step and the shallow is flat…

Thanks for the info, I am going to have it done, and @tester will look at the pan drop and flush option.