Here’s the latest reader question, along with my reply!
Leticia writes: I have a 2017 Mazda 3. It seems like it is skipping when driving in city traffic 20-40MPH. I asked my mechanic. He said it is the way the computer runs the car that causes that. I did not notice this till recently. I first thought it was the tires or the “smart brake” being on. It is annoying. I had a 2016 Mazda 3 and I never had this problem. I don’t believe the 2016 had the smart brake so that is why I was wondering if this is the issue. Any input would be appreciated. I see you on the David Knight show often. That is how I found out about your website. Thank you!
My reply: What you’re feeling is probably the transmission torque converter going into – and out of – lock-up. A torque converter is a device that transfers the engine’s power to the transmission via a fluid coupling. Basically, transmission fluid under pressure (from being spun inside the torque converter, which looks kind of like a donut). This allows slippage – which is why you can stop a car with an automatic with the transmission in gear (as opposed to having to disengage the engine from the transmission, as in a manual-equipped car, but either putting the transmission in neutral or by depressing the clutch).
But slippage is inefficient; it results in a reduction in fuel economy. The fix? A lock-up torque converter, which mechanically (not hydraulically) connects the engine to the transmission once the car is moving.
But, the coupling/decoupling (which is controlled by the computer and may happen when you accelerate, or the transmission shifts gears) can sometimes be felt.
The other possibility is that the transmission is trying to shift up into overdrive (again, for reasons of fuel economy) faster than road speed/loads indicate; this results in the transmission shifting out of overdrive – and back and forth.
And yes, this is normal. It doesn’t hurt anything, but it is annoying.
Which is why I prefer manual transmissions, which only shift when asked!
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