A conservative approach to high mileage transmission flush

Okay I have read the many threads on wether it is better to never touch or throw caution to the wind and everything in between that my head is spinning. So thought I'd throw an approach that I haven't seen mentioned out for comments.
So background. I recently bought a 07 Tacoma SR5 TRD sport 4.0 with 5 speed auto trans and 207k on the odo. I am working on establishing a baseline on maintenance. I attempted to have a fluid flush on the trans at 2 dealers and they refused since there is no record of fluid ever being changed. Bummer.
I'd like to know the condition of the current fluid before I make a decision on which way to go. So I am thinking of doing the following. Add 1/2 qt new fluid to the trans. Bring to temp and drain through the level check drain. This approach does 2 things. Make sure tranny is at proper level, and I should get back some dirty fluid to evaluate condition of the existing fluid and make a somewhat informed decision. This can be done for the cost of 1qt fluid and 2 sealing rings.
Thoughts?

 

Just saying here my first 2nd Gen 2005 DCSB 235,000 I dropped the pan and filter and changed out soon as I got the truck. Ran it till 258, then got totaled but had no issues at all tranny ran great. I don’t believe in the old tales. Living proof right here, and actually helped my shuttering a bit

 

So you're saying 25k miles later the truck quit moving at all? LOL

 

It could move, just needed a nose, but INS paid me 10K

 

I just had it changed today on my truck by Toyota.
Reason being there is no record from the previous owner when they changed it.
So, that is a massive question mark and I too wanted a baseline records.

But I do see evidence it has been changed at some point in its life.

So far, since the auto trans fluid change no shuddering, no grinding etc.

I did the same for my auto Mini Cooper but that was forced onto me, when a plastic drain plug broke. Still no issues after 3 years from that incident.

 

Did they do the flush or drain and fill?

 

I requested a Drain and Fill for now.

As in my mind/hypothesis at least I can keep some of the “old” fluid in there for now to mix with the new stuff.
I wanted to be as minimally invasive as possible. At least for now.

In a 1-2 years time I will ask them to drop the pan, clean up the filter, flush and reinstall. That way both the old and the new fluid has a chance to “break in” and “mix”.

I have no evidence to support my hypothesis/ plan. But it makes sense in my mind.

edit: changing the fluid at least in my experience is a good thing.

 

I understand your plan. I am actually happy the dealer did not do the drain and fill on mine. Once I do my test I will at a minimum drop the pan and change the filter. I want to personally see the condition of pan and contents.

 

I did ask the actual mechanic about the auto filter, he said “Unless there is a lot of metal particles, we just clean it and throw it back in there.”

Make of that what you will.

 

I don't have much experience with automatics, almost all my cars have been manuals.

But here is my experience FWIW. My son worked at a Ford dealer. They took an AMC Pacer as a trade in. Desperate to just get it off the lot they gave it to my son. Awesome right? We drained the trans and what came out looked like mud. Poor car. We dropped pan cleaned and installed new filter 4 times over the next week. Fluid looked like new on final drain. If any high mileage trans was going to fail that one would get my vote. No problem at all with the transmission until it burned to the ground.