Hi, long time viewer, new poster here. I have a 2010 Sienna, FWD, 141k. Vehicle has been maintained throughout its life. Recently when I was driving it on the interstate it started having driving issues. When starting from a dead stop it shifts up from first, second and then the engine overrevs and doesn't want to keep going. If I keep the accelerate down it will eventually "catch" and go up into 3rd gear and continue. When I checked the tranny fluid, it is no long a nice red color but a dark red/brown. The fluid level shows correct on the dipstick. There are NO codes or check engine lights. I dropped the transmission pan today and found no traces of colors in the fluid but a slight sludge on the magnets. I am wondering if I should pull the shift solenoids and test those even though I would think a bad one would show in a obdii scan (I am using a more advanced Autel scanner that is suppose to show transmission codes)? Or should I just replace the filter and fluid and see if that changes things? Could it be a ECM or TCM acting up? Or maybe a torque converter? Any thoughts are appreciated. Thank you in advance.