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fuel efficient overdrive gear/transmission

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Old 07-30-2012, 08:50 PM
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harbin9er
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fuel efficient overdrive gear/transmission

Hi all

noticed the other day that my typical highway cruising speed in 6th gear (manual) is almost 3K RPM
I could get more MPG's if my engine revs were lower during cruise, like say 2K RPM
The MPG's may decrease even further when I downsize my rims from 19" to 18"

does anyone know if there are aftermarket transmissions/solutions where I can get a very tall overdrive 6th gear (Basically I only ever use 6th during cruising)?
Old 07-30-2012, 09:29 PM
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chlutz214
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get a 7AT next time lol, 65 mph cruise is at about 2100
Old 07-31-2012, 01:11 PM
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harbin9er
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hmm yea but auto is not as fun as manual

kinda want the 7 speed manual from the new Porsche 911... wonder how easy it is to shift
Old 08-02-2012, 11:00 AM
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cribbsjy
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Sounds like you need to look into getting a higher final drive (which would be a lower number), but understand that this will stretch out ALL gears, not just 6th. So you will achieve a lower RPM while cruising in 6th, but you will also accelerate slower in every gear.

Perhaps you could start here and contact the seller for more information? Understand that this part is for a 350z/g35, so it might not work >.>
Old 08-02-2012, 11:22 AM
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JSolo
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OP, slow down a bit. 3K rpm is around 80 MPH IIRC. Slow down to 65 and your mpg will increase considerably.
Old 08-02-2012, 04:21 PM
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harbin9er
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@Jsolo - yea, I was speeding a bit. But even at 70mph (the generally accepted cruising speed in ATL), the RPM's are maybe 2500

@cribbsjy
hmm yea... I know of that solution - to make the final drive taller. But like you said that would affect all my other gears.

it seems to me that in terms of actual gear boxes, there aren't that many after market parts available (other than swaps with other stock gearboxes)? It would be interesting to get that Porsche 911 7 speed manual as aftermarket

Just wondering out loud for what I would think would be an interesting upgrade
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