lilbrudder Posted July 14, 2012 Share Posted July 14, 2012 I would like to get more out of fifth gear and be able to cruise at 80MPH under 3000 RPM's...has anyone replaced your fifth gear with a taller one? if so what is involved(parts/labor/prices). Link to comment Share on other sites More sharing options...
LuckyBob Posted July 14, 2012 Share Posted July 14, 2012 Far more money and effort than you'll save in gas over the lifetime of the car, I'm sure. Link to comment Share on other sites More sharing options...
scoobyscoodle Posted July 14, 2012 Share Posted July 14, 2012 Taller tire = taller 5th gear. Link to comment Share on other sites More sharing options...
lilbrudder Posted July 14, 2012 Author Share Posted July 14, 2012 I'm not really going for the fuel economy benifit, that is just a bonus...I really don't like the car reving that high while crusing(sounds like I'm flooring some little car) Link to comment Share on other sites More sharing options...
lilbrudder Posted July 14, 2012 Author Share Posted July 14, 2012 I did get taller tires already, didn't get me as far as I hoped. Link to comment Share on other sites More sharing options...
scoobyscoodle Posted July 14, 2012 Share Posted July 14, 2012 Do a 6MT swap. Link to comment Share on other sites More sharing options...
lilbrudder Posted July 14, 2012 Author Share Posted July 14, 2012 I prefer 5 speed...less gear changes ect. Link to comment Share on other sites More sharing options...
lilbrudder Posted July 14, 2012 Author Share Posted July 14, 2012 Plus,I heard somewhere that the 6 speed has the same final, just more gears to keep you in the power, so not really what I'm looking for Link to comment Share on other sites More sharing options...
scoobyscoodle Posted July 15, 2012 Share Posted July 15, 2012 My rpms at 80 in 6th are lower than a 5mt at 80. Link to comment Share on other sites More sharing options...
Moderators BarManBean Posted July 15, 2012 Moderators Share Posted July 15, 2012 Either way, I you actually did a 6mt swap you could still customize the gears however you wanted before throwing the new trans in right? You could make 6th very specific to highway cruising and leave the other gears to more or less match the 5mt gears. Still though, it's an expensive endeavor. "Bullet-proof" your OEM TMIC! <<Buy your kit here>> Not currently in stock Link to comment Share on other sites More sharing options...
lilbrudder Posted July 15, 2012 Author Share Posted July 15, 2012 Scooby, what is your RPMs at 80? Link to comment Share on other sites More sharing options...
scoobyscoodle Posted July 15, 2012 Share Posted July 15, 2012 The sti 6mt has a slightly lower final drive than the specB I'm pretty sure. I'll have to check my revs at 80, but I wanna say its inbetween 2.8-3k. When I'm going normal freeway speed here in la (65-75) I'm right around 25-2600. I went from LA to SD the other day going 70-75 in 6th and averaged 30-32mpg. Link to comment Share on other sites More sharing options...
lilbrudder Posted July 15, 2012 Author Share Posted July 15, 2012 I may be confused but my OEM service manual shows the same final gear ratio (4.11), doesn't that mean both cars will be spinning the same RPMs at 80mph regardless of it being a 5 speed or 6? Link to comment Share on other sites More sharing options...
Chris GTO TT Posted July 15, 2012 Share Posted July 15, 2012 Not sure on the year but the LGT went 3.90 instead of 4.11 That doesn't mean that 5spd and 6spd cars have the same rpm at the same speed. Final drive ratio, top gear ratio and overall tire diameter together define what the rpm is at highway speed. The spec. B 6spd has a longer top gear than the LGT 5spd, so no matter what it will have lower revs on the highway at any given speed as long as both are in top gear. 2003 Baja 5MT 2016 Outback 2.5i Premium w/Eyesight Link to comment Share on other sites More sharing options...
lilbrudder Posted July 15, 2012 Author Share Posted July 15, 2012 In my car it is still the 4.11. As far as the rpm vs ratio,I was under the impression the final drive determined your speed to RPMs in top gear... I may be wrong,I suppose I should do some reading on that, unless someone wants to explain it. Link to comment Share on other sites More sharing options...
DeltaNu1142 Posted July 15, 2012 Share Posted July 15, 2012 So, one possibility that you're moving towards in this thread & that no one has mentioned is... changing final drive ratio. I know what's involved in a RWD car (I had a C3 Corvette with a 2.73 final drive... a 2.73!), but can it be done in LGT's? It would achieve your goal of having a taller 5th gear without adding shifts. Tits mcgee Link to comment Share on other sites More sharing options...
scoobyscoodle Posted July 15, 2012 Share Posted July 15, 2012 You can't simply change the rear end ratio because it must match the gearing for the front end in the tranny. Link to comment Share on other sites More sharing options...
Chris GTO TT Posted July 15, 2012 Share Posted July 15, 2012 In my car it is still the 4.11. As far as the rpm vs ratio,I was under the impression the final drive determined your speed to RPMs in top gear... I may be wrong,I suppose I should do some reading on that, unless someone wants to explain it. It does but so does the gear ratio of your top gear do a Google search for a gear ratio calculator and plug in the LGT gear ratios for the transmission and final drive ratio. Then play with the final gear ratio and top gear ratio independent of each other. So, one possibility that you're moving towards in this thread & that no one has mentioned is... changing final drive ratio. I know what's involved in a RWD car (I had a C3 Corvette with a 2.73 final drive... a 2.73!), but can it be done in LGT's? It would achieve your goal of having a taller 5th gear without adding shifts. Yes you can do that in the LGT also but it's not as simple as on a RWD where you just swap the ring and pinion in the rear differential. On the LGT (or any other AWD/4x4) you must match the final drive ratio on both axles. In our case that means tearing into the transmission as well as the rear differential or swapping in a transmission and rear differential from a car with a different final drive ratio. 2003 Baja 5MT 2016 Outback 2.5i Premium w/Eyesight Link to comment Share on other sites More sharing options...
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