Help me decide on final gear ratio.

[smokescreens]

I have a 2018 gt pp1 with the torsen diff and 3.73 gears. Car is whippled and a manual. Im looking to lower my cruise rpms about 300ish on the freeway as im running about 2400-2500rpm at cruise now. I dont want to crush my accelerations but i know there is a little trade off. And for any who has done it would i be far off if i estimate $800 to have it done?

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[RagmopInKona]

Why? The mpg gain will be tiny and lugging when you climb an incline at cruise in o.d. will eat any gains . And not do the engine or drivetrain any favors.
Droping rpm from 2500 to 2200 is just going to work it harder at any incline or need to accelerate.

 

[smokescreens]

I get your point. But is 2,200 honestly lugging the engine? With the gearing ratio of the transmision and my tire size 2500 in 5th is 70mph. And i could care less if i cruise in 5th normally. That little extra rpms saving on the freeway cruise at 80-85would make longer drives a better for noise and such. The wife has a hard time with exhaust noise on work calls even with the active exhaust in quite mode. I assume you live in a area with beautiful hills/mountains. But here in SE michigan the land is lame and flat, lol.

I was honestly asking about the lugging point. With the whipple adding the tq it really dont feel like lugging for smaller changes in speed to accommodate for a hill or such. Guess i could go for a drive and really focus on the power delivery at 2200 or maybe just add some sound deadener on the car and call it a day.

 

[boB]

To change rpm by about 10% we can change gearing by the same. Going from 3.73 to 3.55 is not enough, 3.31 is close.

 

[TeeLew]

N/A, people generally like the 3.73 because the engine needs revs. You've got a Whipple, so the extra RPM isn't necessary. The 3.31 will drop cruise revs and make the car nicer to drive, because you won't be shifting as much. Traction in first gear will probably improve and I doubt if the difference in acceleration is even measurable if you're not at the strip.

 

[Cory S]

3.31 would be your GOAT ratio.

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