Angels lex

Hi,I am hoping for some advice on my 99 RX 300...Knock sensor code came up..would go on and off drove the car three days ..and on the third day the tramsmission slipped for the first time ever ..got me home but now it is slipping in forward gears...reverse is good..changed filter and fluid..still slipping in froward gears, have noticed the shift lever can move from first to neutral without pressing the side button...could it be shifter cable...or sensor..or solinoid...please help...

hypervish

Doesn't sound good. How many miles on the car? How often was the fluid changed and what fluid was used?

Angels lex

There are 117000 miles on the transmission. The change of fluid I just did was the second fluid change..the fluid was clean. The drain plugs and magnets had very very little metalic on them..the filter looked clean but I put a new one in just to be sure.There was no metal or any sign of anything unusual in the pan..the new transmission fluid I just added is Castrol Transmax..recommended for Lexus ..it is a high mileage type..thanks for asking I hope this helps