Gear change and speedo

Rattlin_Ram

Rattlin_Ram

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Aug 8, 2007
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Changing gears on my truck to 4.10's what are my options for correcting the speedo? I don't believe the smarty will correct for gear change...
 
I think you should be good to go, the 98+ read off of the tone ring in the back.
 
Really? Mine isn't hooked up right now and I still have speedo... speed sensor was different on the rear end I just put in... Haven't wired it up yet.
 
Might read off of the front Wheel speed sensors then.
The 97 and older used a VSS that was in the tcase.

If your reading off of anything that reads off of the wheels/axle you won't need a change until you change tire sizes.
 
Ring and pinion change and tire diameter change are the same. I bouth cases your speedo will show not actual speed.

Like 3.54 to 4.11 or

31 inch tire to 35 inch tire


I have heard some electronic speedo calibrator are on the market ?
 
AsTroSS said:
Ring and pinion change and tire diameter change are the same. I bouth cases your speedo will show not actual speed.

Like 3.54 to 4.11 or

31 inch tire to 35 inch tire


I have heard some electronic speedo calibrator are on the market ?
Click to expand...

Actually they aren't.

If your reading the speed off of the tone ring or the actual wheel sensor, the speedo could care less how fast the driveshaft is spinning, the sensor will measure the same number of counts per wheel rotation, and if the tire size wasn't changed then it will get the same number of counts per distance traveled.

If you change the tire size the amount one rotation of the wheel does will change the distance traveled. Hence throwing off your speedo.
 
You might be right , it does not care how many rpm engine makes, it only reads tire rotation.

But if you change tires how to readjust PCM for new tire size?

I have 37 tires and my speedo is totally off.
 
AsTroSS said:
You might be right , it does not care how many rpm engine makes, it only reads tire rotation.

But if you change tires how to readjust PCM for new tire size?

I have 37 tires and my speedo is totally off.
Click to expand...


I agree on the tire change, the speedo will need calibrated.
 
Sorry to hijact the thread, but this information might be useful other aswel.


Do you have any idea how to recalibrate speedo?
 
you can calibrate up to 35s by either going to the dealer or using something like a superchips programmer

Superlift makes this box that wires in-line with the VSS and you adjust it to your tire size. From what i heard, it takes a bit longer for the speedo to reach the right speed.

TruSpeed www.superlift.com
 
My SMARTY re-calibrated for my tire size change. I haven't verified if my speedo is correct yet with a GPS, I just figured it was wrong...

I'll check it this weekend...
 
Took the GPS with me on the way to work... it was within 1-2mph... so must be accurate....
 
I did the same swap for gears and the speedo was dead on. Not sure where the speedo reads from...
 
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