4.10 to 4.30 speed difference

Reply Subscribe

Thread Tools

Search this Thread

Nov 21, 2012 | 08:37 AM

andrewzx92000

Thread Starter

Tuned

Joined: Sep 2002

Posts: 408

Likes: 11

From: saline USA

4.10 to 4.30 speed difference

Just went from 4.10 to 4.30 on my V10 two wheel drive with 245/75/16E tires, all stock. What will be the speedometer reading difference. I remember when I went from 3.73 to 4.10 it was about 10 percent at all speeds. The 4.10 to 4.30 change is about half of that in ratio.
Should I assume from that that the percentage of speedo error will be about 5 percent at any given speed.
Please help me with this equasion and thanks for the input
Andrew.

Nov 21, 2012 | 08:54 AM

jeep.hauler

Junior User

Joined: Sep 2008

Posts: 76

Likes: 0

From: San Diego, CA

I have used this in the past to get close and then verified the speed with a gps.

4Lo.com :: Speedometer Check Calculator

Nov 21, 2012 | 08:59 AM

a4t1rat

Senior User

Joined: Nov 2008

Posts: 164

Likes: 1

From: Utah

Well if you figure you tire size is 31" and your over drive ratio is .71 then at 2250 rpm with 4.10 gears you would be going 71.31 mph. With 4.30 gears you would be at 68.0 mph so that is pretty close to your 5% or 3.4 mph

Nov 21, 2012 | 11:08 AM

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

Posts: 24,730

Likes: 2,657

From: SE Florida

Here is the equation:

Current speed * 4.30 / 4.10

So at 70 MPH your speedo will now read 73.4 MPH.

Nov 21, 2012 | 11:20 AM

andrewzx92000

Thread Starter

Tuned

Joined: Sep 2002

Posts: 408

Likes: 11

From: saline USA

Thanks guys, that has helped me, appreciate the responses
Andrew.

Nov 21, 2012 | 11:47 AM

SuperDutyScaler

Lead Driver

Joined: Nov 2008

Posts: 8,450

Likes: 70

From: South Jersey

on a ford super duty absolutely nothing. Ford uses the tone ring on the ring gear to determine speed, even if you change gear ratios the tone ring still sees the same speed. Only thing that changes speed is if you change tire size