guillermo
NAXJA Forum User
- Location
- El Paso, Tx
Just re-geared to 4.11 with 31 in. tires. About how much does this throw off my speedometer ? Just want to avoid getting a speeding ticket. I don't have a GPS. Thanks.
-
Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.
Actual speed
- Thread starter guillermo
- Start date
- Location
- Hammertown, USA
what year / transmission?
guillermo
NAXJA Forum User
- Location
- El Paso, Tx
2000 automatic 4.5 lift
WB9YZU
NAXJA Forum User
- Location
- Madison, WI
Given RPM, Transmission Gear Ratio, Rear Gear Ratio, and Tire Size, you can get MPH.
So...
MPH=(RPM * Tire Diameter)/ (Gear Ratio * 336)
So, if you measure your RPMs in 3rd gear, you only have to figure the rear end ratio because 3rd is 1:1.
Example: Stock rear ratio, automatic engine RPMS are 2300, running 31" tires.
(2300*31)/(3.55*336)=59.7mph
At the same RPM, you'd be going about 51.6 MPH with 4.11 gears.
So...
MPH=(RPM * Tire Diameter)/ (Gear Ratio * 336)
So, if you measure your RPMs in 3rd gear, you only have to figure the rear end ratio because 3rd is 1:1.
Example: Stock rear ratio, automatic engine RPMS are 2300, running 31" tires.
(2300*31)/(3.55*336)=59.7mph
At the same RPM, you'd be going about 51.6 MPH with 4.11 gears.
- Location
- Hammertown, USA
http://www.4lo.com/calc/gearratio.htm
3rd gear = 1:1 transmission ratio
4th gear = .75:1 transmission ratio
So put:
tire diameter = 31
transmission = .75
Transfercase = 1
Dif = 4.10
Then fill in MPH for how fast you want to go, and click calculate.
55 mph will be 1833 RPM's in 4th gear
You will have to clear RPM's to set a new MPH to recalc.
65 will be 2166 RPM's
75 will be 2500
and so on.
3rd gear = 1:1 transmission ratio
4th gear = .75:1 transmission ratio
So put:
tire diameter = 31
transmission = .75
Transfercase = 1
Dif = 4.10
Then fill in MPH for how fast you want to go, and click calculate.
55 mph will be 1833 RPM's in 4th gear
You will have to clear RPM's to set a new MPH to recalc.
65 will be 2166 RPM's
75 will be 2500
and so on.
4LowandGo
NAXJA Forum User
- Location
- Kennesaw, Georgia
http://www.speedometerservice.com/
For less than thirty bucks shipped you can fix the problem and not have make any calculations. All you need to do is find out what tooth gear you need and then order a new speedo gear.
I drove for over a year by doing the calculations and then went out and spent about 25 bucks to get a new speedo gear. My only complaint was that I wish I did it sooner.
For less than thirty bucks shipped you can fix the problem and not have make any calculations. All you need to do is find out what tooth gear you need and then order a new speedo gear.
I drove for over a year by doing the calculations and then went out and spent about 25 bucks to get a new speedo gear. My only complaint was that I wish I did it sooner.
hubs97xj
NAXJA Forum User
- Location
- Fort Wayne, IN
guillermo
NAXJA Forum User
- Location
- El Paso, Tx
Thanks for all your responses... I will order the new "gear" today.
