As the title suggests, my 2001 LS430 seems to have a non-cooperative gearbox. For example, when I am going up a rather steep hill in 4th gear and I want a bit more power so I press the gas pedal harder to get it to kickdown into 3rd, when I do that, the car seems to stutter and hesitate and the gearbox would not change down. It kind of feels like the gearbox had a go at changing into 3rd, then gave up and stayed in 4th. If I keep the throttle angle the same, the car would keep stuttering every second or so, almost like its misfiring. I would have to keep giving it more gas and then it would downshift 2 gears and off I went. I don't really want to kickdown 2 gears everytime I want to go a bit faster cos then I would be going too fast. I have cleaned the maf sensor which helped the throttle response but the gearbox problem persists. I have d&f the trans fluid once after I purchased it and am planning to do it again very soon.
Any ideas? Would appreciate any advices! Thanks!

 

If the kick-down problem occurs to all speeds (5→4, 4→3, 3→2, 2→1), the likely culprit is your ECM. However in your case, you're dealing with kick-down from 4th to 3rd. Most likely, you have a sluggish/clogged No.3, or No.4 (or both) shift solenoids.

 

Rkw77080 are you a Lexus master tech? You give a lot of amazing tech answers. Bravo!

 

Thanks for the kind words, but no, I'm not a Lexus master tech. I have a 2003 and a 2004 LS430 in my garage. I do all the maintenance and repairs myself, and through the years, I have learned a lot from other members on this forum.