rear end gear question
05-26-2008, 03:30 PM
#2
2nd Gear Member
Join Date: May 2008
Posts: 213
RE: rear end gear question
On the highway, drive at an even 60 mph and have someone (not you) record the RPMs (try to be accurate).
Then, plug it into this equation:
Gear Ratio = (RPM*Tire Diameter)/(MPH*336)
So, assuming a 25.7 in wheel diameter, and a ratio of 3.73, your RPMs should be about 3,000. If it's higher or lower, you know you're not at 3.73.
Then, plug it into this equation:
Gear Ratio = (RPM*Tire Diameter)/(MPH*336)
So, assuming a 25.7 in wheel diameter, and a ratio of 3.73, your RPMs should be about 3,000. If it's higher or lower, you know you're not at 3.73.
05-26-2008, 04:42 PM
#4
4th Gear Member
Join Date: Jun 2007
Location: Ohio
Posts: 1,996
RE: rear end gear question
or just check out this site made by the intelligent CliffyK
http://www.paladinmicro.com/PalMFrame00.htm?wks= Look on the left hand side for RPM vs. Speed, it should be all the way at the bottom.
http://www.paladinmicro.com/PalMFrame00.htm?wks= Look on the left hand side for RPM vs. Speed, it should be all the way at the bottom.
05-26-2008, 05:05 PM
#5
4th Gear Member
Join Date: May 2008
Location: Santa Monica, CA
Posts: 1,842
RE: rear end gear question
I'm pretty sure with 3.73's your not gonna be at 3k at 60mph. I read somewhere that you'll be at like 2005rpm. Which kinda makes sense since the 3.73's are considered an all around choice and 3000 at 60mph sounds really too high to me lol
Brandon
Brandon
05-26-2008, 05:07 PM
#6
4th Gear Member
Join Date: Apr 2008
Location: KS
Posts: 1,016
RE: rear end gear question
or you could put your back end on jack stands and with it in nuetral, mark driveshaft location and tire location (tape, chalk, etc.) then rotate the tire and count its revolutions in perspective to the driveshafts revolutions to be accurate you would have to spin the tire 100 times.
05-26-2008, 05:15 PM
#7
4th Gear Member
Join Date: Jun 2007
Location: Ohio
Posts: 1,996
RE: rear end gear question
ORIGINAL: StriderTacticaL
I'm pretty sure with 3.73's your not gonna be at 3k at 60mph. I read somewhere that you'll be at like 2005rpm. Which kinda makes sense since the 3.73's are considered an all around choice and 3000 at 60mph sounds really too high to me lol
Brandon
I'm pretty sure with 3.73's your not gonna be at 3k at 60mph. I read somewhere that you'll be at like 2005rpm. Which kinda makes sense since the 3.73's are considered an all around choice and 3000 at 60mph sounds really too high to me lol
Brandon
05-26-2008, 05:18 PM
#8
3rd Gear Member
Thread Starter
Join Date: Apr 2006
Location: Canton, Mi
Posts: 741
RE: rear end gear question
i went to that site.. at 50 in 4th im at 2500rpm on the dot, 50 in 5th at 1700rpm and at 80 im at 2700rpm. if u change out gears does it make the speedo off?
edited: 4th gear 60mph 3k rpms
edited: 4th gear 60mph 3k rpms
05-26-2008, 06:19 PM
#9
4th Gear Member
Join Date: Jun 2007
Location: Ohio
Posts: 1,996
RE: rear end gear question
Yes a gear change will make the speedo off unless it has been corrected by some sort of tune, but it sounds to me like your running 3.73's and that the speedo has been corrected either by a speedcal box or a chip with a tune on it, unless you have a handheld.
05-26-2008, 06:59 PM
#10
3rd Gear Member
Thread Starter
Join Date: Apr 2006
Location: Canton, Mi
Posts: 741
RE: rear end gear question
no i dont.. i dont wat was done to this car before i got it.. all i know it had 24k miles on it.. had bbk cold air kit, bbk headers, bbk off road H, 40 series flows, the 3.73s and idk wat else has been done .. i was thinkin of getting a dyno and a tune..