WOT kick-down button question

[nickclk430]

I have a 99 430 with 98K miles and when I hit the gas hard and depress the kick-down button sometimes it revs up to like 5-6K RPM's and takes off like a bat out of hell other times at the same speeds it goes up to about 4K RPM's and still takes off fast and delays up shift but obviously without such jerk as when it hits 5-6K RPM's. I was wondering if my kick-down is faulty or if something else could be going on. It seems like it doesn't downshift when it only goes to 4K but that is is just accelerating with the extra gas but when it goes up to 5-6 it is definitely downshifting

[sfclk]

sounds like it's working fine. when downshifting to 4k, the transmission probably goes to the lowest gear under 6k rpm.