Changing the Gear Ratios to get better fuel economy?
 

If I had a Toyota Yaris would it be possible to change the gear ratio to get better fuel economy? I know it costs more to change the gear ratio but would there be a cheap fix? Like getting bigger wheels/rims to obtain better fuel economy on the highway?

This is a question that I've pondered many times, because my car is geared far too low for its engine. The only way for it to be cost-effective is to put on bigger tires when your tires are worn out, but you won't be able to go much larger without it looking ridiculous (and possibly driving badly -- I can imagine 1st gear being too tall).

I suppose if you expect to get 200,000 miles or more out of your car, the investment in gears could pay off. I will only have this car for less than 50,000 miles, so that wouldn't work for me.

I have a hunch changing the gears would void my warranty. Intriguing speculation, though. I've wondered what installing an overunning clutch would involve. Always considered it in the context of putting in a smaller engine, though.

I changed out the gears in my truck and it cost about a grand. I did it for speed not for fuel economy. you could do it but it would take a while to get your money back on that one. also, if they don't make the gears to swap out, having custom gears cut is stupid expensive.

another thing to consider is that you will have to drop the trans to get to your gears (I think) because it is a front wheel drive vehicle. they just had to pull my axles and remove the diff cover for me. not sure about having to drop the trans but I still think it is more complicated with a front wheel drive car.

it would be awesome if you did it. I have been thinking of a yaris myself, if you find something that would work, keep us posted.

First of all, don't think that you have every possible gear ratio sitting on the shelf and you can just order it. In reality, you are probably stuck with ratios from the factory in other Yari (Yaruses?).

Even then, it's not just gonna be that you unbolt a gearset and bolt in a new one, as if you had a '70's musclecar.

Even if you can find a new Yaris transaxle, you'll also need to reprogram the computer, as this does require the gear ratio to do everything correctly.

I'd be surprised if you saw a payback in less than 250k miles...

-Bob C.

why would you have to do anything with the computer?

I assume you mean with an automatic which may be true but with a stick shift, I thought that the only change would be the speedo and the odo readings.

I do agree with you that the payback would be very lengthy. there was a guy on here (metrompg I think) that swapped in a different trans into his metro but he was given the trans or it was really cheap (cant remember which) and had great success with it. his situation is different.

my truck didn't care other than the fact that I was running 2600rpms at 70 mph and it launched like nobody's business. 29 inch tires and 4.10s in the rear.

Ahh, gear swaps. Your best bet for gear swaps was the Corolla but the Yaris uses the C54, not the C56 that the Corolla has.

It wouldn't be a stock swap anyways because the Yaris has more gearing than the Corolla, probably due to the taller tires.

how fast is the yaris's rpm buzzing at 60 mph? about 2000?

How much better fuel economy would you hope to get out of a Yaris? My sister-in-law has a 2008 4 door 5 speed manual Yaris and she gets 41+ MPG every single tank and she doesn't even employ any crazy FE tactics.

In a FWD yes you will have to pull the transmission to change gears or final drive ratio. IT most certainly gives better FE but as mentioned, how long does it take to pay off. I've collected a pile of tires (actually 4 8' stacks) and can change them at school so that part's easy and it changes my odometer mileage by 14% which is good for 3 mpg where it's sitting (18 mpg changes to 21) (no rings to speak of and the wrong transmission so OD is 10% too short)

As for transmission gear interchangeability in the Yaris, it's entirely possible the C54 and C56 gears are interchangeable. older toyota transmissions (namely the W5x series that I have in the Cressida) are identical except for different gear ratios which is why I have the wrong transmission: literally indistinguishable except 5th gear is .85 in the W57 I have instead of .76 in the W58 I have to put in.