2000 540iA Transmission Shift Problems

just started having an intermittant shift problem a couple of days ago, the car is having difficulties shifting from 2 to 3rd gears. from a dead stop the car will shift from 1st to 2nd no problem, its hard to upshift to 3rd until about 3.5-4k rpm. if i put the car in sports mode, triptronic, i can shift to 3rd but it will want to down shift back to 2nd. it will not want to shift into 3rd until i hit about 4k rpm, then it will finally shift.

the transmission shifts through the gears smoothly, up & down. there seems to be no catching, or abrupt shifting. i'm suspecting its not the transmission itself but some sensor or electrical issue. i recently replaced the ccv, front intake gasket, manifold gaskets & various vac lines. not sure if this could have been a cause.

i've done a forum search & google search, found that the front abs sensor/speed sensor will sometimes cause this hiccup. also, found that the ecu could be the culprit or low tranny fluid. last i checked, fluid level was fine. will be checking the sensor next. is there anywhere or anything else i should be looking? any help or suggestions? thanks!!!
cheers,
larry

^bump...

can someone please confirm for me which front abs sensor controls the transmission shifting operation? from my understanding its the passenger front. thanks!!!
cheers,
larry