I bought a new to me T4R 4th gen (2007 model) SR5 4WD. Single owner with great service records. Single owner and verified 150k mostly highway miles (lots of oil changes in two alternating cities, 500 miles apart per the car fax). The truck is solid and I love it.

Unfortunately, I've found no records of the automatic transmission ever being serviced.

My mechanic (who is a bit old school TBF, but I trust him) told me to not change the transmission fluid. I planned to drop the pan & filter and replace what comes out (rather than do a "flush").

What are your thoughts? 150k is high milage to me, but among you guys it seems like mine is barely broken in. I dont want to replace the trans prematurely.

Worth noting that it shifts through all gears smoothly, including reverse. No reason to second guess it other than I always change fluid and trans filter AT LEAST every 50k (even on "lifetime units" like my wifes VW).

Thanks!! This community is awesome

Change your fluid. The top picture is what my trans fluid looked like after @100k miles over 11-12 years. It's on the left. The spot on the right is the color that drained out of my ride after I flushed it. The bottom spot is new from the bottle. Then there's the bottom picture of my transfluid. It looked like motor oil

Your trans needs new fluid and the best way to do it is by a fluid exchange. Search transmission fuid exchange on this board and you will find a wealth of info. It's not hard and it's good insurance for your truck.

The only reason would drop the pan is the clean it out and see what's on the magnets. Dont bother changing the screen/filter.

With mostly highway driving the WS fluid can go to 120k easy. You're getting to the point where it may be a good idea to swap it. Then again, my 3rd gen sits at 234k with mostly orginal fluid in the trans. Lost a quart or two when the radiator blew.

Definitely change the fluid using the fluid exchange method. Use Toyota WS fluid

I'm for the "do" change it boat.

Bought my 07 with 142k on the clock. Did the lazier 3 D/F over a few thousand miles to refresh the ATF.

Used Maxlife ATF if you cared to know.