MPV1 VCM Editor Gear/Tire Calculator Producing Erroneous General Speedometer Figures.

[fivetears]

NOTE: My vehicle speed is monitored by a stand-alone GPS speedometer; not a PCM controlled indicator. That stated...

When entering my actual tire size & gear ratio (37.7" / 4.56:1) in the Gear/Tire Calculator, the MPV1 VCM Editor mis-calculates my VSS pulse per mile. it reads as follows under the General tab:
VSS Pulses per mile: 97.574
Final Drive Ratio (4.56) Transmission Revolutions/Mile: 2,592.5972

My Manual Mathematical Calculations:
There are 63,360 inches in a mile.
My 37.7" Tire will hypothetically travel 118.378 inches per each rotation; 37.7 * 3.14 = 118.378
If 118.378 inches is equal to 40 VSS pulses, then:
There are 535.234587507814 VSS pulses per mile; not 97.574

I humbly realize my tuner is antiquated, but it is all I have. How do I correct / align the incorrect VCM Editor Speedometer General Tab entry values generated by the Gear/Tire Calculator? They are clearly way off and my 4L60E shift scheduling is less than optimal. I figure these basic entries here may have something to do with my shift timing dis-satisfaction.

[fivetears]

NOTE: My vehicle speed is monitored by a stand-alone GPS speedometer; not a PCM controlled indicator. That stated...

When entering my actual tire size & gear ratio (37.7" / 4.56:1) in the Gear/Tire Calculator, the MPV1 VCM Editor mis-calculates my VSS pulse per mile. it reads as follows under the General tab:
VSS Pulses per mile: 97.574
Final Drive Ratio (4.56) Transmission Revolutions/Mile: 2,592.5972

My Manual Mathematical Calculations:
There are 63,360 inches in a mile.
My 37.7" Tire will hypothetically travel 118.378 inches per each rotation; 37.7 * 3.14 = 118.378
If 118.378 inches is equal to 40 VSS pulses, then:
There are 535.234587507814 VSS pulses per mile; not 97.574

I humbly realize my tuner is antiquated, but it is all I have. How do I correct / align the incorrect VCM Editor Speedometer General Tab entry values generated by the Gear/Tire Calculator? They are clearly way off and my 4L60E shift scheduling is less than optimal. I figure these basic entries here may have something to do with my shift timing dis-satisfaction.

[fivetears]

Attached the ,HPT file in work.

[fivetears]

I'm not the greatest mathematician.
If a 4L60E VSS gets triggered 40 times per driveline rotation, and a 37.7" tire travels 118.378 inches per rotation, and the tire gets rotated 4.56 times per driveline rotation, then the tire travels 539.80368" per driveline rotation. Right?

So that would be 63360" divided by 539.80368" = 117.3760060324153 VSS PPM

Still not 97.574
What am I missing now?
Does 19.80200603241534 missing VSS pulses even matter in the grand scheme of shift scheduling?

[TransGo Robert]

I'm not the greatest mathematician.
If a 4L60E VSS gets triggered 40 times per driveline rotation, and a 37.7" tire travels 118.378 inches per rotation, and the tire gets rotated 4.56 times per driveline rotation, then the tire travels 539.80368" per driveline rotation. Right?

So that would be 63360" divided by 539.80368" = 117.3760060324153 VSS PPM

Still not 97.574
What am I missing now?
Does 19.80200603241534 missing VSS pulses even matter in the grand scheme of shift scheduling?

To calculate the pulses per rotation accurately you cannot use t circumference of the tire, you have to use the loaded radius. Since that can't be measure by most people easily, the calculator uses the revolution per miles published by tires manufacturer for each tire circumference, which in this case is 535. This is plenty good enough, since in real life the number of revolution per miles will always vary a bit with tire inflation differences and tire wear.

[fivetears]

Appreciate it Robert.
National Wheel & Tire's website has a basic drivetrain chart that covers tire circumferences ranging from 17.5" to 54."
Never knew such a chart existed. it has a 38" tire rotating 545 times per mile; no variables mentioned though.
https://ntwonline.com/tire-shop-talk...er-mile-chart/