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Prius Transmission

Your description of the CVT in the Prius, in your article, in the drive section of the East Bay Times on March 5th is wrong.

The the transmission in the Prius is composed of several planetary gear sets which allow the car to be driven by various combinations of the two electric motors and the gasoline engine.

I don’t think Tom or Ray will be responding, but if you’d like to provide a link to the article, I’d be happy to discuss it.

@ProVega350 - I read that column in my paper, also, and agree that he got it wrong. Oddly, I can’t find it in the ‘Dear Car Talk’ section:

@Whitey - Ray answered a letter asking about driving habits in a Prius, and he mentioned that it has a CVT (correct) that uses a belt and pulleys (incorrect).

I’ve heard Tom and Ray describe a CVT transmission that way on their radio show back in the day, and when they did, they used words like “basically” to describe how a CVT operates to the average layman who calls into the show (or reads the column) and doesn’t know what a planetary gear is.

I agree that from a technical perspective of someone who really understands how a CVT works, it’s not technically correct, but for the majority of the column’s readers, explaining the concept of a belt around a conical pulley that slides back and forth to change the gear size demonstrates the concept of what makes a CVT more efficient than a traditional automatic transmission.

It’s important to remember that Car Talk’s target audience isn’t the knowledgeable DIYer or the experienced mechanic, it’s the average Joe who doesn’t know much about cars, and to them, there is no benefit to learning what a planetary gear is and how it works. When it comes to explaining things to those who aren’t knowledgeable, it’s best to avoid technical jargon and explain the concept in terms the listener/reader can grasp.

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That would be one planetary gear set.

Saw an 07 Prius for sale that owner says needs a new torque converter. He said trans was rebuilt <1yr ago but they did not replace convertor. I would think a hybrid that uses elec assist for acceleration in conjunction with gas motor/trans would be hard to diagnose for those issues.

Hmm…that Prius owner is very confused. It has no torque converter, another advantage to the ‘Synergy Drive’. Non-hybrids with belt CVTs do have torque converters.