Speedo recalibration?
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Elder User
Joined: Oct 2006
Posts: 554
Likes: 0
From: Everett, PA
Speedo recalibration?
Hey all, I was just wondering how I go about adjusting my speedo for accurate mpg readings? I'm running a 3.73 gear right now with 325/65r18 tires. If I adjust it with the sct and set the axle ration on it to a 3.55 will it be accurate again. I'm also stepping up to a 4.30 gear soon and was wondering if I set it to 4.10s when I do that will it be accurate or should I just have Ford recalibrate it for me? Thanks!!
Lead Driver
Joined: Jun 2007
Posts: 6,757
Likes: 5
From: Corvallis, OR
Gear settings don't affect the speedometer because its read off the axle, only tire size affects it. Also, there is only a handful of tuners that can adjust the speedometer, it needs to recalibrate the abs module to do this. The SCT does not have this ability yet, but I've heard its close. As soon as they add that support I'll be buying one. Until then, I'm happy running with it about 7-8% off, which is all yours should be off by. Your other options are to get one of those wire-in speedo calibrators such as the Superlift Truspeed or a couple others, these are especially handy if you change tire sizes in winter or when offroading. Also, Ford can recalibrate it, but only up to 34.5" tires for some reason.
Fleet Mechanic
Joined: Nov 2004
Posts: 1,427
Likes: 10
From: Templeton, Massachussetts
Gear settings don't affect the speedometer because its read off the axle, only tire size affects it. Also, there is only a handful of tuners that can adjust the speedometer, it needs to recalibrate the abs module to do this. The SCT does not have this ability yet, but I've heard its close. As soon as they add that support I'll be buying one. Until then, I'm happy running with it about 7-8% off, which is all yours should be off by. Your other options are to get one of those wire-in speedo calibrators such as the Superlift Truspeed or a couple others, these are especially handy if you change tire sizes in winter or when offroading. Also, Ford can recalibrate it, but only up to 34.5" tires for some reason.
So you saying the ring gear spun off a smaller pinion will read the same as stock gearing??
Lead Driver
Joined: Jun 2007
Posts: 6,757
Likes: 5
From: Corvallis, OR
The speedo signal comes from a sensor ring mounted on the ring gear, so it only changes based on axle speed (tire size), gears do not affect the speedo reading. The revs/mile input on the X3 is for shift points, it does not alter the speedo.
Fleet Mechanic
Joined: Nov 2004
Posts: 1,427
Likes: 10
From: Templeton, Massachussetts
I see what your saying, it is a BRAB-130 part #, used to replace them all of the time.I was not sure on the SCT III since I never used that portion..Mine is fairly acurate since I got a ticket for 110 in a 55MPG zone when I first installed the hybrid file..
