Someone explain GEARS to me
03-12-2012, 07:43 PM
#21
You can probably hit 140 with 4.10's, but you RPMs would be really high.
When you think of gears think of it like this. Let's say you have 4.10's. The small pinion gear has 10 teeth and the big ring gear has 41. That means the small pinion gear attached to the drive shaft will have to spin about 4 times to make the big ring gear (attached to the wheels) spin once. That lets your engine rev up higher and quicker before delivering the full power to the wheels.
If you have a 2.73 gear set, your small pinion gear now has 15 teeth and the big gear still has 41, but now it only takes 2.73 rotations of the pinion to get the ring gear to make a full rotation. That means the engine can't rev up as high before it gets into the power-band.
That's about as clear as mud, I know.
When you think of gears think of it like this. Let's say you have 4.10's. The small pinion gear has 10 teeth and the big ring gear has 41. That means the small pinion gear attached to the drive shaft will have to spin about 4 times to make the big ring gear (attached to the wheels) spin once. That lets your engine rev up higher and quicker before delivering the full power to the wheels.
If you have a 2.73 gear set, your small pinion gear now has 15 teeth and the big gear still has 41, but now it only takes 2.73 rotations of the pinion to get the ring gear to make a full rotation. That means the engine can't rev up as high before it gets into the power-band.
That's about as clear as mud, I know.
03-12-2012, 08:30 PM
#22
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What kind of 1/4 mile time can I expect if I upgrade to 3.42's or 3.73's? Does it just feel faster? Or does it actually considerably up your car's quickness/acceleration?
03-12-2012, 11:31 PM
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It actually takes stress off the transmission by going to a higher gear? Hmm, even more reason to do that then.
What kind of 1/4 mile time can I expect if I upgrade to 3.42's or 3.73's? Does it just feel faster? Or does it actually considerably up your car's quickness/acceleration?
What kind of 1/4 mile time can I expect if I upgrade to 3.42's or 3.73's? Does it just feel faster? Or does it actually considerably up your car's quickness/acceleration?
03-13-2012, 05:24 AM
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It actually takes stress off the transmission by going to a higher gear? Hmm, even more reason to do that then.
What kind of 1/4 mile time can I expect if I upgrade to 3.42's or 3.73's? Does it just feel faster? Or does it actually considerably up your car's quickness/acceleration?
What kind of 1/4 mile time can I expect if I upgrade to 3.42's or 3.73's? Does it just feel faster? Or does it actually considerably up your car's quickness/acceleration?
Your sig say's white a4 with 2.73s?? just wondering
03-13-2012, 05:35 AM
#25
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It'll just "feel" slightly faster...maybe a tenth in the 1/4. I personally wouldn't spend the money for a 3.42 to 3.73 swap. Not really worth it, unless your maxed out on mods and trying to squeeze every last bit of torque you can get.
Your sig say's white a4 with 2.73s?? just wondering
Your sig say's white a4 with 2.73s?? just wondering
03-14-2012, 08:43 PM
#29
My complaint is that the steps between a few common gearings is so insignificant that it doesn't really matter. (say 2.73's to 3.23's, or 3.23's to 3.42 ect), so my question has always been, why would you pay a few hundred dollars for a 3.73 gear for an A4 car when low mileage used 3.42 gears can be had for $30-50 all day long?
If the answer is "for the extra performance", that's stupid IMO, because everyone knows in these cars the rear ends turn into glass when you make any kind of real power (sometimes even under stock power).
Thats why my opinion is, if you really feel like you want a gear upgrade, but don't want to drop the cash on a whole new rear end, get a set of 3.42's for super cheap and enjoy the slight performance gain. Anything beyond that isn't going to be much more of a performance upgrade anyway, and that few hundred bucks you would have spent on 3.73 or 4.10 gears should just go to the rear end fund (along with the saved gas money
)A few viable reasons to get a gear upgrade would be to match your stall/cam setup, or to dictate what RPM you cross the finish line at (for instance to prevent the car from taking the time to shift into 4th gear before the 1/4 mile ends), but even then, those are obviously for cars that spend a lot of time at the track, which should probably have 9"s or 12 bolts anyway for any serious duty.
03-14-2012, 09:33 PM
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OK, gears essentially make the car feel faster, with maybe a couple tenths max in the 1/4 as others have said.
My complaint is that the steps between a few common gearings is so insignificant that it doesn't really matter. (say 2.73's to 3.23's, or 3.23's to 3.42 ect), so my question has always been, why would you pay a few hundred dollars for a 3.73 gear for an A4 car when low mileage used 3.42 gears can be had for $30-50 all day long?
If the answer is "for the extra performance", that's stupid IMO, because everyone knows in these cars the rear ends turn into glass when you make any kind of real power (sometimes even under stock power).
Thats why my opinion is, if you really feel like you want a gear upgrade, but don't want to drop the cash on a whole new rear end, get a set of 3.42's for super cheap and enjoy the slight performance gain. Anything beyond that isn't going to be much more of a performance upgrade anyway, and that few hundred bucks you would have spent on 3.73 or 4.10 gears should just go to the rear end fund (along with the saved gas money)
A few viable reasons to get a gear upgrade would be to match your stall/cam setup, or to dictate what RPM you cross the finish line at (for instance to prevent the car from taking the time to shift into 4th gear before the 1/4 mile ends), but even then, those are obviously for cars that spend a lot of time at the track, which should probably have 9"s or 12 bolts anyway for any serious duty.
My complaint is that the steps between a few common gearings is so insignificant that it doesn't really matter. (say 2.73's to 3.23's, or 3.23's to 3.42 ect), so my question has always been, why would you pay a few hundred dollars for a 3.73 gear for an A4 car when low mileage used 3.42 gears can be had for $30-50 all day long?
If the answer is "for the extra performance", that's stupid IMO, because everyone knows in these cars the rear ends turn into glass when you make any kind of real power (sometimes even under stock power).
Thats why my opinion is, if you really feel like you want a gear upgrade, but don't want to drop the cash on a whole new rear end, get a set of 3.42's for super cheap and enjoy the slight performance gain. Anything beyond that isn't going to be much more of a performance upgrade anyway, and that few hundred bucks you would have spent on 3.73 or 4.10 gears should just go to the rear end fund (along with the saved gas money
)A few viable reasons to get a gear upgrade would be to match your stall/cam setup, or to dictate what RPM you cross the finish line at (for instance to prevent the car from taking the time to shift into 4th gear before the 1/4 mile ends), but even then, those are obviously for cars that spend a lot of time at the track, which should probably have 9"s or 12 bolts anyway for any serious duty.
03-14-2012, 09:39 PM
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03-14-2012, 09:44 PM
#32
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GR is both transmission ratio and axle ratio multiplied together...
If you have an A4 auto trans:
GR = 2.73 * 1.000 (3rd gear) or 2.73 * 0.696 (4th gear)
If you have an M6 manual trans:
GR = 2.73 * 1.000 (4th gear)
TD is the diameter of your tire (from tread to tread) = 25.6"
so then your calculation would be either of these:
70 * 336 * (2.73 * 1.000) / 25.6 = 2508 rpm (A4 3rd gear, or M6 4th gear)
70 * 336 * (2.73 * 0.696) / 25.6 = 1746 rpm (A4 4th gear)
If you have an A4 auto trans:
GR = 2.73 * 1.000 (3rd gear) or 2.73 * 0.696 (4th gear)
If you have an M6 manual trans:
GR = 2.73 * 1.000 (4th gear)
TD is the diameter of your tire (from tread to tread) = 25.6"
so then your calculation would be either of these:
70 * 336 * (2.73 * 1.000) / 25.6 = 2508 rpm (A4 3rd gear, or M6 4th gear)
70 * 336 * (2.73 * 0.696) / 25.6 = 1746 rpm (A4 4th gear)
03-14-2012, 09:47 PM
#33
The other option would be to just keep your eyes out for an affordable 3.42 rear end. They pop every once in a while and Ive seen them as low as $300 for the entire rear (thats still less than you'd pay to buy 3.73 gears new and have a shop install them) if you do the labor yourself, which isn't all that hard.
03-16-2012, 10:23 PM
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OK, gears essentially make the car feel faster, with maybe a couple tenths max in the 1/4 as others have said.
My complaint is that the steps between a few common gearings is so insignificant that it doesn't really matter. (say 2.73's to 3.23's, or 3.23's to 3.42 ect), so my question has always been, why would you pay a few hundred dollars for a 3.73 gear for an A4 car when low mileage used 3.42 gears can be had for $30-50 all day long?
If the answer is "for the extra performance", that's stupid IMO, because everyone knows in these cars the rear ends turn into glass when you make any kind of real power (sometimes even under stock power).
Thats why my opinion is, if you really feel like you want a gear upgrade, but don't want to drop the cash on a whole new rear end, get a set of 3.42's for super cheap and enjoy the slight performance gain. Anything beyond that isn't going to be much more of a performance upgrade anyway, and that few hundred bucks you would have spent on 3.73 or 4.10 gears should just go to the rear end fund (along with the saved gas money)
A few viable reasons to get a gear upgrade would be to match your stall/cam setup, or to dictate what RPM you cross the finish line at (for instance to prevent the car from taking the time to shift into 4th gear before the 1/4 mile ends), but even then, those are obviously for cars that spend a lot of time at the track, which should probably have 9"s or 12 bolts anyway for any serious duty.
My complaint is that the steps between a few common gearings is so insignificant that it doesn't really matter. (say 2.73's to 3.23's, or 3.23's to 3.42 ect), so my question has always been, why would you pay a few hundred dollars for a 3.73 gear for an A4 car when low mileage used 3.42 gears can be had for $30-50 all day long?
If the answer is "for the extra performance", that's stupid IMO, because everyone knows in these cars the rear ends turn into glass when you make any kind of real power (sometimes even under stock power).
Thats why my opinion is, if you really feel like you want a gear upgrade, but don't want to drop the cash on a whole new rear end, get a set of 3.42's for super cheap and enjoy the slight performance gain. Anything beyond that isn't going to be much more of a performance upgrade anyway, and that few hundred bucks you would have spent on 3.73 or 4.10 gears should just go to the rear end fund (along with the saved gas money
)A few viable reasons to get a gear upgrade would be to match your stall/cam setup, or to dictate what RPM you cross the finish line at (for instance to prevent the car from taking the time to shift into 4th gear before the 1/4 mile ends), but even then, those are obviously for cars that spend a lot of time at the track, which should probably have 9"s or 12 bolts anyway for any serious duty.
I'm suggesting if your going to spend the money on NEW gears with an a4Then get your moneys worth...3.73s.
