Anyone running a 4.09 rear gear ratio ?

MRGTX

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Reviving this thread as it looks like there's more to be said on this topic.

I am finally getting close to the end of my break-in period on my 2020 GT 6spd and I'm starting to realize that the transmission feels great to shift (yeah, I am enjoying the feel of the MT-82. I said it! :D ) and the deeper I get into the power band of the engine, the more I love it...but as stated earlier, it looks like the new ratios steal a chunk of the fun of driving a manual performance car.

It's even worse for those of us with the 3.55 axle...and I'm starting to see this mod, at least for those of us with non-PP cars, to be a requirement for the car to fulfill its promise as a sporty/muscle car.

Here are the questions that I need to answer before I take the plunge:

1.) How much worse will the fuel economy be? Is anyone smart enough to do a back of the napkin calculation on the increased RPM and energy losses to friction? If it's significant enough, it could be a factor...especially as fuel prices will certainly go up over the period of time that many of us will own these cars as daily drivers.

2.) How would the ratio impact the longevity of the motor? Would you shorten our oil change interval? Does it notably increase the amount of heat that the cooling system has to deal with? Does this mean that non-PP owners need to budget for the PP radiator?

3.) Would Ford void your warranty for this?

4.) Most importantly, Is it worth it?? What is the new ratio like to drive? Does it measurably improve performance?
 

maddog1982

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Watched this yesterday, I really wish they hadn't made this change
 

cib24

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1.) How much worse will the fuel economy be? Is anyone smart enough to do a back of the napkin calculation on the increased RPM and energy losses to friction? If it's significant enough, it could be a factor...especially as fuel prices will certainly go up over the period of time that many of us will own these cars as daily drivers.
Negilgible. The gear ratios are still so wide you won't notice any difference at all when driving, and RPMs are only 285 RPMs higher at 70 mph compared to running the stock 3.55 ratio. See below the cruising RPMs and max speeds at 7400 RPM in each gear.

upload_2019-7-4_10-15-56-png-png-png.png


2.) How would the ratio impact the longevity of the motor? Would you shorten our oil change interval? Does it notably increase the amount of heat that the cooling system has to deal with? Does this mean that non-PP owners need to budget for the PP radiator?
Negligible if not at all. Your oil life gauge will tell you when to change the oil if you like to use that. No extra heat, it's all fine.

3.) Would Ford void your warranty for this?
No.

4.) Most importantly, Is it worth it?? What is the new ratio like to drive? Does it measurably improve performance?
Obviously. Without it your 2018+ GT is slower than a 15-17 GT with less horsepower up to about 80 mph due to their better gearing.
 
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Alfa Male

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Watched this yesterday, I really wish they hadn't made this change

Interesting video and makes a lot of sense. Obviously this is based on the manual GTs having a 3.73 ratio whereas we are stuck with the 3.55 which is even worse.

Sort of reconfirms my thoughts on the need to play with the gear ratios.
 
 
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