740 turbo auto shifts too soon

Fluid level is correct though recently repaired a leaky line that drained 3 pints.
323k on odometer.
Won't stay in high gear under 55mph.
I seem to recall there's a cable adjustment at throttle but not sure how to proceed
with adjustment.
Your 2 cents appreciated!

Yes, it's called the kick-down cable.
Some pointers here: https://forums.turbobricks.com/showthread.php?t=340755&highlight=kick+adjustment

Brickboard says: https://brickboard.com/FAQ/700-900/TransmissionAuto.htm#Kickdown_Cable_Adjustment