If you checked at the Lexus site and it doesn't show an ATF flush/change, that might not mean it wasn't done by the previous owner, of course. But my habit every time I have bought a new-to-me car (13 or 14 cars and trucks over the years, can't remember any more), is always to change all the fluids first thing, or within a few months of buying it. Knowing little or nothing about the previous owner's maintenance habits I assume they were lazy, cheap and ignorant and never changed a thing except the oil (MAYBE). And then just change them all.

I got my 2017 LS in May 2023. I bought a case of Toyota WS ATF fluid and took it to a transmission shop. They charged me $250 to change it. But did they? They could have parked it for a few hours, stolen some of the ATF and gave it back to me untouched for all I know. But since there's no practical way for me to tell obviously I had to trust them. Even so, I had a Valvoline quicky lube change the ATF yet again less than a year later.
So fingers crossed, between those two shops hopefully somebody changed something in the transmission...did I double my chances by having it done twice? (Again, no way for me to tell without some fluid analysis, the cost of which would be counter-productive...so who knows?)

I realize now doing it that way was pretty dumb. For the cost of doing it twice I could probably have just bought an ATF flush from a dealership instead, which is what I should have done. But I wanted to get the fluid changed at least, before the car hit 100,000 miles (It was about 70,000 miles at the time). Next time I'll have the dealer flush the ATF, maybe when it hits 100,000 miles...

Well, my valve body had damage in the B2 circuit check valve. It was galled up in there. I bought a new valve body from Lexus and installed it and this resolved my issues. I bought it during the 4th of July sale and with tax and free shipping it was about $1k. I also need to change the output seal on the transmission, but cannot find one anywhere, and even Amayama doesn't list a part number for it. It seems that Lexus only provides it in the overhaul kit, but I do not need to overhaul the transmission to change an old seal. Napa, Oriellys, Autozone etc.. all do not have a listing for this seal. Does anyone have the part number for the output seal?

thanks for the update

Here?

https://www.japan-parts.eu/lexus/us/...unter-gear-atm

looks like you found it
https://www.clublexus.com/forums/ls-...rt-number.html