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**Gregski** · 08-26-2019, 10:28 PM

HP Tuners - Part III - Change Tire Size and Gear Ratio

In this section we will take care of two things to make the automatic transmission shift points happy, we will enter our tire diameter and our rear diff gear ratio. You can use the link below to enter your tire specs to get the diameter if you can't do it in your head, ha ha.

Tire Size Calculator

We will also enter the proper Gear Ratio, 3.73 was a popular ratio, but yours will vary, there may be a taggie tag on your pumpkin if you're lucky telling you what your gears are.

I know I preach making one change at a time but we have to use our common sense, if the settings are related it's ok to combine them, wouldn't you agree? (For example later on we will disable codes for both rear O2 sensors in one fell swoop instead of two separate configs, it just makes sense.)

1. Again we start in the comfort of our own home, we fire up our laptop and launch the Editor. Open the file we saved in Step 3 of Part II. (Now this is your new base file, assuming that it all worked last time, see how this works now?).

2. Make changes in the Editor, this time we will make two simple changes since they go hand in hand, we need to change the Tire Size, in my example I use 28.9" (235/75-R15) and the Gear Ratio, mine was 3.73.

3. Save the changes you made to a new file and call it something like "03 - VATS Disabled V8 Tach Signal Tire Size Gear Ratio"

4. Now you get to move the operation to your truck, hook up your HP Tuner to the OBDII port and then your USB cable to your laptop, turn the key to the ON position, launch the Editor program, and simply write the new changes to the PCM.

Note: sometimes you have to write the entire tune file to the PCM, sometimes it is perfectly happy with only writing what's changed, more on this later.

More words with each pic:

I like to call this First Series Housekeeping, the Second Series will focus on disabling the error codes for the components we deleted during our swaps: O2 Sensors, EGR for pre 2002 donor vehicles, EVAP, Fuel Level/Pressure, etc. stay tuned!

08-26-2019, 10:28 PM	#33
Gregski Post Whore Join Date: Aug 2014 Location: Sacramento, CA Posts: 10,803	Re: HP Tuners Tutorials - Part III - Change Tire Size and Gear Ratio HP Tuners - Part III - Change Tire Size and Gear Ratio In this section we will take care of two things to make the automatic transmission shift points happy, we will enter our tire diameter and our rear diff gear ratio. You can use the link below to enter your tire specs to get the diameter if you can't do it in your head, ha ha. Tire Size Calculator We will also enter the proper Gear Ratio, 3.73 was a popular ratio, but yours will vary, there may be a taggie tag on your pumpkin if you're lucky telling you what your gears are. I know I preach making one change at a time but we have to use our common sense, if the settings are related it's ok to combine them, wouldn't you agree? (For example later on we will disable codes for both rear O2 sensors in one fell swoop instead of two separate configs, it just makes sense.) 1. Again we start in the comfort of our own home, we fire up our laptop and launch the Editor. Open the file we saved in Step 3 of Part II. (Now this is your new base file, assuming that it all worked last time, see how this works now?). 2. Make changes in the Editor, this time we will make two simple changes since they go hand in hand, we need to change the Tire Size, in my example I use 28.9" (235/75-R15) and the Gear Ratio, mine was 3.73. 3. Save the changes you made to a new file and call it something like "03 - VATS Disabled V8 Tach Signal Tire Size Gear Ratio" 4. Now you get to move the operation to your truck, hook up your HP Tuner to the OBDII port and then your USB cable to your laptop, turn the key to the ON position, launch the Editor program, and simply write the new changes to the PCM. Note: sometimes you have to write the entire tune file to the PCM, sometimes it is perfectly happy with only writing what's changed, more on this later. More words with each pic: I like to call this First Series Housekeeping, the Second Series will focus on disabling the error codes for the components we deleted during our swaps: O2 Sensors, EGR for pre 2002 donor vehicles, EVAP, Fuel Level/Pressure, etc. stay tuned! Last edited by Gregski; 11-10-2019 at 05:47 AM.