Gear change without calibration

[Odd Ball]

5.13 gears are being installed as I write this post. Although I have purchased the Ford Performance Calibration Tuner, I’m just curious as to how the vehicle will perform with the new gears prior to installing the calibration tune. Any experience out there?

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[Aonarch]

Shift points will probably be wonky, and speedo will obviously be off.

 

[Johnkn]

5.13 gears are being installed as I write this post. Although I have purchased the Ford Performance Calibration Tuner, I’m just curious as to how the vehicle will perform with the new gears prior to installing the calibration tune. Any experience out there?

The answer depends on whether you've changed the tire size from OEM.


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[Odd Ball]

The answer depends on whether you've changed the tire size from OEM.


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38”

 

[Johnkn]

38”

Then use a speed calculator and plug in your OEM tire diameter and gears and compare to the new diameter and gear set.

Here's one:

Vehicle Speed Calculator (spicerparts.com)


Unless you've moved to much lighter wheels you've likely added a lot of unsprung weight to each corner which will be noticeable. The calculator will let you know how close to OEM speed you'll be at a given RPM with the new wheels and tires.


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[Odd Ball]

Then use a speed calculator and plug in your OEM tire diameter and gears and compare to the new diameter and gear set.


Here's one:

Vehicle Speed Calculator (spicerparts.com)

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I’m not exactly sure what I would get out of that. I was just wondering if anyone had any experience and if the vehicle felt jerky or awkward in anyway. I plan on using the calibration unit within a day or two of picking up my truck anyway. Just curious…

 

[dgorsett]

Assuming 4.70s and 35s to start 5.13and 38 = 8% ish and 8 % ish so no calibration needed. Bronco speedo aren't close to start with.

 

[Bmadda]

Vehicle speed is calculated by ABS and reads off the wheels, so the gear change wont affect the speedo. The AT shift strategy may be a little off, but doubt that will be enough to be a problem. AT has an output speed sensor to determine if there is slippage in the trans, so it may be confused by the mismatched values vs ABS and set a code...but other than that (which I doubt) doubt you will be able to tell the difference

 

[Odd Ball]

Vehicle speed is calculated by ABS and reads off the wheels, so the gear change wont affect the speedo. The AT shift strategy may be a little off, but doubt that will be enough to be a problem. AT has an output speed sensor to determine if there is slippage in the trans, so it may be confused by the mismatched values vs ABS and set a code...but other than that (which I doubt) doubt you will be able to tell the difference

Thanks. Apparently the ABS doesn’t like tires greater than 37”. I guess I’ll be “close”.

 

[Bikeric]

Thanks. Apparently the ABS doesn’t like tires greater than 37”. I guess I’ll be “close”.

You cannot input anything over 2800mm for circumference using Forscan. Not sure what calibration tool you’re using, but I’ll assume it’s outputting a value above that number.

 

[Bmadda]

Thanks. Apparently the ABS doesn’t like tires greater than 37”. I guess I’ll be “close”.

That's kinda where I am at too...within 4mph, which is close enough for me!

 

[Odd Ball]

You cannot input anything over 2800mm for circumference using Forscan. Not sure what calibration tool you’re using, but I’ll assume it’s outputting a value above that number.

Ford

You cannot input anything over 2800mm for circumference using Forscan. Not sure what calibration tool you’re using, but I’ll assume it’s outputting a value above that number.

Ford Performance Procal 4. Same…

 

[Brian_B]

Vehicle speed is calculated by ABS and reads off the wheels, so the gear change wont affect the speedo. The AT shift strategy may be a little off, but doubt that will be enough to be a problem. AT has an output speed sensor to determine if there is slippage in the trans, so it may be confused by the mismatched values vs ABS and set a code...but other than that (which I doubt) doubt you will be able to tell the difference

This.

I tried cheating the ratio to get around the 37” limit and it didn’t affect the speedo at all

 

[Oldhippie]

The Procal seems let ya go more 37s

 

[Bmadda]

The Procal seems let ya go more 37s

100% when I had 37s on mine (which measured out pretty true to size) I was able to get my speedo dead nuts w/gps speed. I think 578 rev/mile was the sweet spot, but can't remember for sure. It sets a U0422 code in the PCM because that's a value outside the PCM's normal parameters, but I had zero problems, and perfect speedo accuracy. Now with 40s I am off a smidge...I think I set it at the lowest value it would accept, and it's still reading a little slow

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