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Has anyone change their rear ring and pinion on their 4x2 to try for better fuel mileage. If so what are the results?
 

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What type of gear ratio change do you think might improve fuel economy? Higher? Lower?

Unless your driving conditions are far outside the norms for a street-driven FJ, its unlikely that any gearing change will improve fuel economy.

Toyota went to extreme lengths to optimize fuel economy on all FJ models to meet the Federal CAFE standards, and its unlikely that you can make any mechanical changes that will improve that, except for installing narrower, street-tread tires, removing the roof rack, removing the spare tire and the rear seats to reduce weight, etc. 99% of any improvement will come from your right foot.
 

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As you probably know it has a stock 3:72 gear I was thinking of lowering to as low in the 3s as I can get. It turns 2900 rpms @ 73 mph.
 

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What type of gear ratio change do you think might improve fuel economy? Higher? Lower?

Unless your driving conditions are far outside the norms for a street-driven FJ, its unlikely that any gearing change will improve fuel economy.

Toyota went to extreme lengths to optimize fuel economy on all FJ models to meet the Federal CAFE standards, and its unlikely that you can make any mechanical changes that will improve that, except for installing narrower, street-tread tires, removing the roof rack, removing the spare tire and the rear seats to reduce weight, etc. 99% of any improvement will come from your right foot.
I am not sure I agree with that statement above. While I agree tires and weight will help increase your mileage, your gear ratio will help.

When I had my Ford Mustang I went from factory 3:27 gears to 3:73 to 4:10 and finally ended up with 4:30 gears. Mileage suffered each time. Granted once I went 4:10's in was more a race car then a daily driver but nevertheless I could be driven on the street.Therefore, the concept of lowering your gear ratio since most 4x2 FJ's don't see a lot of off road action in "theory" should work.

It becomes more of a question is it worth it ??
 

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I am not sure I agree with that statement above. While I agree tires and weight will help increase your mileage, your gear ratio will help. (snip)

Therefore, the concept of lowering your gear ratio since most 4x2 FJ's don't see a lot of off road action in "theory" should work.
Lowering the final drive ratio to get better fuel economy?? That's just going to increase engine RPM at cruise, which is unlikely to improve fuel consumption.

Going the other direction might have some small possibility for improvement at the cost of more sluggish response. Then again, Toyota has carefully calibrated the transmission shift points for economy, and changing the final drive ratio in either direction might upset that careful balance.
 

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Lowering the final drive ratio to get better fuel economy?? That's just going to increase engine RPM at cruise, which is unlikely to improve fuel consumption.

Going the other direction might have some small possibility for improvement at the cost of more sluggish response. Then again, Toyota has carefully calibrated the transmission shift points for economy, and changing the final drive ratio in either direction might upset that careful balance.
Actually going up will not help but again in theory going down should help. RPM's will go down. With a higher ration the faster you climb in MPH the higher RPM goes. For example at 60mph you might be at 2k rpm if you go up at 60mph you might be 3.5k RPM If you go down 1 notch from factory it should have you at about 1.5k RPM. However, you need a 6 speed tranny not 5 speed.
 

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Actually going up will not help but again in theory going down should help. RPM's will go down. With a higher ration the faster you climb in MPH the higher RPM goes. For example at 60mph you might be at 2k rpm if you go up at 60mph you might be 3.5k RPM If you go down 1 notch from factory it should have you at about 1.5k RPM. However, you need a 6 speed tranny not 5 speed.
You've got your gear-ratio nomenclature backwards.

A "higher" gear ratio is a numerically smaller value.

For example, a 3.23:1 ring and pinion set is a "higher" gear ratio than a 4.56:1 ring and pinion. In top gear at any given speed, the engine will be turning at lower RPM with a 3.23:1 gearset than with a 4.56:1 gearset.
 

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You've got your gear-ratio nomenclature backwards.

A "higher" gear ratio is a numerically smaller value.

For example, a 3.23:1 ring and pinion set is a "higher" gear ratio than a 4.56:1 ring and pinion. In top gear at any given speed, the engine will be turning at lower RPM with a 3.23:1 gearset than with a 4.56:1 gearset.
I meant lower. Sorry! Lol
 

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As you probably know it has a stock 3:72 gear I was thinking of lowering to as low in the 3s as I can get. It turns 2900 rpms @ 73 mph.
That's hard to believe. I don't think you are in high gear. Assuming it's an automatic transmission, it sounds like you're in fourth gear. Bump the shifter over to get fifth gear and you'll drop to 2,000 rpm.
 

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As you probably know it has a stock 3:72 gear I was thinking of lowering to as low in the 3s as I can get. It turns 2900 rpms @ 73 mph.
There is absolutely no question you've got you gear selector in the wrong position.

First of all, the transmission is a 5-speed.

Look at the markings on your shift gate: "4-D". In this position, the shift lever can be moved left or right to two possible selections:
1. To the left, in the "4" position, which prevents the transmission from shifting higher than 4th gear;
2. To the right, which allows the transmission to shift into 5th gear.

Being in 4th gear at 70 MPH gives an engine speed of 2800 -2900 RPM, depending on tire size. No wonder you are getting crappie fuel economy; how long have you been driving around at freeway speeds while locked in 4th gear?
 
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