Does anyone know what kind of problem of my CVT trans has ? I got the transmission replaced a year ago and since then I keep driving it and it has no problem whatsoever. But about 3 months ago I started to notice that when I let go for the gas peddle for the car to cruise alone the rev idle will somehow goes up by almost 1k rpm, and then when I push the gas paddle again try to accelerate it goes down again. And this situation happens sometimes but not every time. And I also noticed that if I go downhill and let the car cruise alone the rev idle will go up quite a lot up to almost 2.5k rpm. I know something is happening to the car but it do rent show and fault code. I try test drove my friend’s LS600 and it doesn’t have this problem. Right now I’m sort of thinking maybe is the clutch plate or the flywheel gone bad. Since I know this model can experience a bad flywheel. And also the car will jerk a bit every time I accelerate to 50mph mark and after a sec it keep going smooth with no problem.

 

I don't have a 600h (*not yet anyways*) but wild guess it sounds like the transmission fluid level issue? Maybe when they put the new unit in they didn't refill it enough? Like there's some parts of your CVT that aren't getting the correct pressures to positively engage the gears. So maybe taking it to a Lexus dealer to have them check fluid level would fix the issue? (or check it at home if that's easy?) Also do you know if they did a TCU relearn process at the time they replaced it?

 

If the revs start to climb when you go downhill this is normal behavior assuming the battery is reaching full charge. Normally the charging system's generation function will bleed speed away excess speed. Once the battery is full this is no longer possible, so to avoid using the brake the hybrid system will use engine breaking (spin the engine with the throttle closed) to hold the car's speed. Stepping on the gas increases the desired speed and reduces the need for engine braking so the revs will drop. So this covers the second case (going downhill) and possibly the first case if you are coasting downhill at all with a full battery.

Hope that helps.

 

Jainla's description is very good. While using cruise control coasting down a hill if your hybrid battery is starting to show its age this will also cause engine breaking more often. An aging battery can't hold as much charge. This may be why your car displays this behavior but your friends doesn't.

 

these transmissions rarely if ever fail. Was yours abused by the previous owner or something?