should I switch to synthetic atf?

No it would just blend and keep diluting as you drain/fill more in the later future

 

Agreed. I'm sure that when I switched to synthetic there was still a good amount of the non synthetic fluid in the system. Has not been an issue and I switched years ago. A few drain and refills since then too.

 

Yeah for a complete switch......I bought one of those $18 12v hydraulic/diesel oil transfer pumps off amozon....
pulled the cooler lines, dumped one side while pumping fresh right back in other line - while running....
I ran twenty qts of max life($130)......for a 9.5 qt system with torque convert.

That's the definition of OCD.

 

At first twenty qts sounds extremely excessive, but that's more or less 4 drain and fills.. which is only 1 more than I would think necessary... I'm going to do two and see how it goes. Nothing wrong with the transmission, and I want to keep it that way.

 

Same with my differential, switched to valoline synthetic, ran it for 5 or 6 mo and then flushed again....

I think your math is off, your tranny has about 5.5 qts in it....
however there is another 4 in the torque converter.....which wont drain out...
it has to be pushed out.

 

drain and fill = 4.5 - 5.5qts (5qt average).

20 (quarts total) / 5 (quarts average drain and fill) = 4 (drain and fill cycles).

I'm not a math major... but that checks out.

I understand that a drain and fill does not replace all the fluid in the transmission system (pan, torque converter, carrier lines, and trans radiator). Which is why I was asking those that have come before me if they experienced an issue running part non-synthetic and fully-synthetic fluid.

Anyway. I got the answer I needed. Drain, fill, and send it.

 

Here's pretty much what I did to get it allllllll......ruby red.

(13) BEST Method Transmission flush '95-'04 Toyota Tacoma √ Fix it Angel - YouTube