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Drive ratio - 4.27 vs. 4.46 on road driving experience difference?

HoosierDaddy

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Which explains why no difference in MPG between the various final ratios ??
That’s what most are saying. Nominal difference in MPG.
For comparisons sake, those monster Sasquatch tires will have a much larger effect on fuel mileage then a couple tenths of a point in gear ratios discussed here.
The 4.70's will equalize almost everything else, but the weight and rolling resistance will drag those MPG numbers down...plus the suspension lift is a MPG penalty also.
4.27 vs 4.46 and no other drive line changes??? 32" tires, Ford 10spd auto.
Let's take a look.
(Edit to add that this came from http://www.grimmjeeper.com/gears.html )


Road RPMs at given speed in miles per hour103570
Gear 4.27
12103736214723
2133846839366
396233686735
480628195639
568023814762
657320054010
744815663133
838013312663
930910812161
1028610022005
R2179762815256



Road RPMs at given speed in miles per hour103570
Gear 4.46
12197768915378
2139848929783
3100535177035
484129455890
571024874973
659820944188
746716363272
839713912781
932311292258
1029910472094
R2276796715934
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Gquag

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Can someone explain in simple terms the difference in on-road driving experience for these drive ratios ?
Tire size counts!
 
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Goat4454

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For comparisons sake, those monster Sasquatch tires will have a much larger effect on fuel mileage then a couple tenths of a point in gear ratios discussed here.
The 4.70's will equalize almost everything else, but the weight and rolling resistance will drag those MPG numbers down...plus the suspension lift is a MPG penalty also.
4.27 vs 4.46 and no other drive line changes??? 32" tires, Ford 10spd auto.
Let's take a look.


Road RPMs at given speed in miles per hour103570
Gear 4.27
12103736214723
2133846839366
396233686735
480628195639
568023814762
657320054010
744815663133
838013312663
930910812161
1028610022005
R2179762815256



Road RPMs at given speed in miles per hour103570
Gear 4.46
12197768915378
2139848929783
3100535177035
484129455890
571024874973
659820944188
746716363272
839713912781
932311292258
1029910472094
R2276796715934
Doesn’t seem like much of a difference. Thanks
 

dgorsett

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The driving experience as far as torque multiplication and RPM is affected by the circumference of the tire in addition to the final ratio. With equal sized tires you will get 9.6% more RPM at the same vehicle speed with the 4.46 gears. You also get an extra 9.6% torque applied at the hub of the wheel. It is a mechanical advantage. Like using a longer wrench on a bolt. It twists the bolt harder with the same force on the handle, but the handle moves further. Imagine a 8 inch wrench; you crank on a bolt and it won't budge. So you go get a wrench that is twice as long, now the bolt turns pretty easily. Double the length of the wrench, double the twist (torque) on the bolt. 10% longer wrench moves the free end 10% more (RPM) and twists the center of the wheel 10% harder. That is what your gearing does. With the same size tire, if the 4.27 gearing had you running 2300 RPM at 60 MPH, the 4.46 would be spinning at 2300 * 1.096 or 2521 RPM. 221 RPM higher. At 80MPH would be 3067 and 3361 RPM respectively at 294 RPM more. Not a huge difference, but probably an MPG or two lower.

Part two is wheel circumference. A larger wheel/tire takes less revolutions than a smaller one to be traveling at the same MPH. if one tire is 50 inches around the outside, it will spin twice as many times as a 100 inch circumference one would in the same amount of time at the same speed, that would halve your RPM at the same speed.

Now, here is the key; if you have two gears about 5% different (like the 4.46 to the 4.70) and put a 5% bigger circumference tire on the lower gear (paradoxically the lower gear has the higher number) they effectively cancel the gearing differences. As it happens the Sasquatch tire circumference is just about 5% longer than the Badlands 33" tire. So the Sasquatch tire on the 4.70 gears will have almost exactly the same RPM at the same speed as the 33" tire on the 4.46 gears.

You can look up the circumference of different tires and then subtract the percentage difference from that 9.6% gearing difference to get the actual percent difference and figure out RPM differences from there. It is easy if it is the same tire, 9.6% difference.

Short version; higher numbered gears multiply torque more. More power at the ground for a given MPH. It also raises the RPM at that given MPH.. Tire sizes can change how much different the power at the ground and the RPM. Not really power, but it is close enough
Yes, and with the same size tire 4.27's to 4.46 would be like using that 8" wrench verses an 8.4" wrench
 

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Goat4454

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good info here. Sounds very minimal difference
 

AZSky

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Base is 4.46 with Manual and 3.73 with AT. Which one would take easier changing the tires to 32" or 33" ?
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