My CVT is beeing strange.

[nielshm]

My car has done 20.000 miles, and I'm starting to see small problems with my CVT transmission. Normal behavior is like this: From 0 the acceleration starts. At some point around 40 mph, the CVT shifts into a sort of overdrive, wich lowers rpm with 500, while the acceleration still continues. If the acceleration is slow, it happens sooner, If acceleration it's hard, it's later. It gives a nice feel to the car and CVT, that something is done to prevent high revs. But something is starting to go wrong: Sometimes the car 'forgets' what to do, and the pleasant feel of overdrive never occurs. The problem persists until the car is shut off and restarted. I've noticed, that it's happening more frequent in the last couple of months. It took a while to figure out what going on, and it's hard to take the car to the dealer, since they most likely wont experiense any problems. Further more, a petrol Auris, non hybrid, with CVT, is pretty rare, and they probably dont have much experiense in sorting out issues like this. 

[FROSTYBALLS]

The Auris has had petrol (non hybrid) CVT's since December 2012, so they cannot be that unusual. Plus other models have combined petrol engines and CVT's - eg. IQ since 2009, and Yaris since 2011.

[nielshm]

Here's a short video clip, showing normal behavior. Revs actually drops 700 rpm. When the car is beeing strange, revs don't drop. 

 

[YarisHybrid2016]

It is the torque converter locking up (it increases fuel efficiency).

The drop in RPM is because there are losses when it is unlocked so the engine runs a slightly higher RPM. When it locks up, the engine doesn't need to work quite so hard, and so the RPM drops.

If it fails to lock up and you can drive at say 50 or 60 MPH, try just gently increasing/decreasing power. If it is still unlocked, the RPM will fluctuate without a change in speed. If it is locked, the speed will change, too.

Note that as it is a CVT gearbox however, it might be difficult to tell.

Is the car in warranty? If you're really concerned, take it to a garage and ask them to look at it. Be sure to drive it with them - you'll know better when it is not behaving itself, and be sure to take them for an extended drive (I had a similar problem on my old not-Toyota car - in that case it was a 4 speed automatic gearbox with torque converter and was obviously malfunctioning).