Hello,
I don't know if anyone can shed any light on this but worth a shot, I suppose.
I don't have a Lexus but a Toyota Aurion 3500cc V6 (2007 model) but people tell me it's similar to a Lexus 350, I dunno.
I just had the ATF fluid changed with Toyota T iv original fluid. The guy drained the transmission and added a whole 4 liter tin of it.
Straight after I noticed a difference in the drive and the changing through the gears...it's not as smooth, quick and responsive as it was before. It feels almost a little sluggish and kind of heavy and sometimes when I push the gas pedal it takes a couple of seconds to pick up speed, then suddenly the rev counter needle shoots up.
I don't know how else to describe it.
What could be the reason?

 

The 5th generation of the ES has the 2gr-fe 3.5 v6. It has a sealed auto transmission (no dipstick) and uses WS fluid, not the older type 4.

https://www.clublexus.com/forums/es-5th-gen-2007-2012/680314-es350-diy-transmission-fluid-change.html

 

Now take all the oil out and fill it with WS.