Calibrating the built-in COMPUSHIFT Speed

The COMPUSHIFT built-in calculated speed is determined by 3 factors. If any of these are out then an incorrect speed will be displayed. This will also have a major affect on when the transmission shifts and when the torque converter locks up.

These factors are:

1. Rolling Tyre Diameter
2. Final Drive Ratio (Diff Ratio)
3. VSS Pulse count (TOSS)

Calibrating these 3 factors to your vehicle correctly is an absolute CRITICAL first step, the calculated speed reported by the COMPUSHIFT must match a GPS speedo with a tolerance of +/- 1kph, when tested at 60km/h (35mph) and at 100km/h (60mph).

If after setting the Tire Diameter and Final Drive Ratio correctly, then generally the VSS Pulse Count is the last variable. This may require removing the TOSS sensor and counting the landings to confirm the number of pulses per revolution.

Rolling Tyre Diameter

Specifically the rolling tyre diameter of your vehicles tires taking into consideration the weight of the vehicle.

Do Not calculate from the specified tire size (eg 265/75R16) as this will give you the diameter unladen. We need the diameter as it is on the vehicle with its current weight on the wheel.

Easiest way to work this out is to measure from the ground to the centre of the axle, then double the measurement.

Enter this into the Tire Diameter setting under Vehicle Setup. If the value is out by a long way, you can tap on the value directly to bring up the keyboard and enter the correct number instead of pressing up/down arrows.

Final Drive Ratio

Essentially this is the ratio of your Differential. For the most part, this should be the standard ratio fitted by the manufacturer, however some vehicles may have had a different ratio fitted for various reasons. This makes it difficult to know exactly what to use for this setting. However, if in doubt, always start with the OEM specification. If the speed does not line up, then you may need to revisit this setting.

List of Standard Diff Ratios for Toyota Vehicles:

• Landcruiser 40 = 4.11
• Landcruiser 60 = 4.11
• Landcruiser 70 & 75 = 4.11
• Landcruiser 78 manual (split transfer case) = 4.3
• Landcruiser 78 manual = 4.10
• Landcruiser 80 = 4.10
• Landcruiser 100 manual = 4.3
• Landcruiser 100 auto = 3.9
• Hilux diesel = 4.88
• Hilux petrol = 4.5

List of Standard Diff Ratios for Nissan Vehicles:

• GQ 2.8 Diesel = 4.625
• GQ 3.0 Petrol = 4.11
• GQ 4.2 Petrol Auto = 3.9
• GQ 4.2 Petrol Manual = 4.11 or 3.9
• GQ 4.2 Diesel = 4.11
• GU 2.8 Diesel = 4.625
• GU 3.0 Turbo Diesel Auto = 4.375
• GU 3.0 Turbo diesel Manual = 4.11
• GU 4.2 Diesel = 4.11
• GU 4.2 Turbo diesel (wagon) = 3.9
• GU 4.2 Turbo diesel (ute) = 4.11
• GU 4.5 Petrol = 4.11
• GU 4.8 Petrol manual = 4.375
• GU 4.8 Petrol auto = 3.54

Pulse Count

With the exception of the A340 and 4L60(variants) transmissions, the pulse count is set and unlikely to be incorrect. But for some transmissions, this pulse count number is adjustable due to variations that we can not account for. If you are unsure of your transmissions pulse count, remove the TOSS sensor and rotate the output shaft one revolution while counting the number of landings.