AWD Gear Ratios

[dbsb3233]

Not really sure there's been much discussion about this, but I got curious when I saw in the order guide posted yesterday the part about different gear ratios between front and rear axles on the AWD (9.05 on the rear and 10.0 on the front). It led me to another article to help explain it...

https://cleantechnica.com/2019/07/22/ev-transmissions-are-coming-and-its-a-good-thing/

I presume that's what the Mach-e is doing too - directing more power to the front motor when traveling at high speeds and less to the rear (after having reached speed) to mimic a higher gear where it consumes less power than it would running completely at the lower gear ratio? Which should help high-speed efficiency relative to what it would be all at the same gear ratio.

Seems like a great idea, although it seems like an even wider differential in gear ratio would be even better.

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[dbsb3233]

I also wonder what they mean by "Final" Drive Ratio? "Final" meaning they tested different ones and that's what they finally settled on? If so, it's kinda weird they'd put that qualifier in the order book that way.

 

[ChasingCoral]

I also wonder what they mean by "Final" Drive Ratio? "Final" meaning they tested different ones and that's what they finally settled on? If so, it's kinda weird they'd put that qualifier in the order book that way.

Maybe there are multiple step-down gears, so they are only listing the final drive ratio, not each step?

 

[JamieGeek]

Yeah final ratio would be the ratio between the motor's shaft and the wheel's axle.

I would think a wider gear ratio would make the car more efficient but have less grunt off the line--it is a Mustang after all.

 

[dbsb3233]

Maybe there are multiple step-down gears, so they are only listing the final drive ratio, not each step?

I wondered that too but I hadn't heard anything about it being variable. I usually hear that being touted for BEVs - no variable gear transmission needed, simplifying the drive train. Or maybe I misunderstood.

 

[dbsb3233]

Yeah final ratio would be the ratio between the motor's shaft and the wheel's axle.

I would think a wider gear ratio would make the car more efficient but have less grunt off the line--it is a Mustang after all.

But even the rear motor alone produces impressive acceleration off the line, without even needing help from the front motor. (Of course, that's a matter of taste - some want even more than "impressive", which is why they're making the GT).

For an all-around vehicle that tries to merge being a Mustang with an SUV, I'd be quite happy with 6.5 second 0-60 from the rear motor and then much better mileage from a high-gear front motor cruising at 70 MPH. Although I don't know enough about it to tell whether a wider drive ratio gap would really do that or not. Just kinda speculating.

 

[SnBGC]

Not sure what the transmission looks like in the MME but they usually have a gear on the rotor, a counter gear and then the differential carrier. Add all the ratios together gets the final drive ratio.

Generally speaking, smaller motors have higher RPM limits. The final drive ratio determines the max vehicle speed at that RPM limit.

I would expect the GT to have the same final drive ratio front to back since the motor is believed to be the same and thus have the same max RPM limit.

 

[SD_Solar]

My 2019 Leaf SL+ has a 8.19 ratio but is driving 17” wheels compared to the Mach-E’s 19”.

Still with only 214 HP / 250 ft-lb compared to the Mach-E’s 346 HP / 428 ft-lb it will jump out enough to earn a dirty look and “are you trying to give me whiplash” comment from my wife.

I don’t think I will be doing max accelerations with the FE and her onboard.

 

[ChasingCoral]

My 2019 Leaf SL+ has a 8.19 ratio but is driving 17” wheels compared to the Mach-E’s 19”.

Still with only 214 HP / 250 ft-lb compared to the Mach-E’s 346 HP / 428 ft-lb it will jump out enough to earn a dirty look and “are you trying to give me whiplash” comment from my wife.

I don’t think I will be doing max accelerations with the FE and her onboard.

Maybe one with a warning?

 

[KAustin]

Maybe one with a warning?

Where is the fun with that?

 

[TheSteelRider]

I also wonder what they mean by "Final" Drive Ratio? "Final" meaning they tested different ones and that's what they finally settled on? If so, it's kinda weird they'd put that qualifier in the order book that way.

Yeah, legacy compared to ICE vehicles. Your transmission will contain the initial drive ratios, a different ratio for each gear. This reduces the engine RPM down by some ratio into the drive shaft.
Then, your drive shaft enters the differential where it undergoes yet another (fixed) gear ratio, usually on the order of 3 to 4 for most "Normal" consumer cars. So, "final" means the "last" gear ratio before the wheels.

 

[TheSteelRider]

Here is a great Engineering Explained video about gear ratios

 

[TheSteelRider]

Jason just did another video about gear ratios for the new Ford Bronco, and throws in some engine vs. wheel torque information as well, so I this new video combined with the original above really gives a comprehensive understanding of gears

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