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Toyota Diff Mounted Trigger Wheel

Page history last edited by wilbo666 10 years, 4 months ago

Introduction
Issue
Diff Mounted Trigger Wheel Drawings
1. Toyota A Series Differential Mounted Trigger Wheel
References

Introduction

When replacing the automatic transmission from Toyota 2JZ-GTE VVTi engines with a manual transmission and retaining the factory engine ECU some difficulty arises in regards to the engine ECU speed sensor as the engine ECU speed sensor is removed with the automatic transmission.

This page details information regarding this issue and one solution to provide a speed sensor signal to the engine ECU - a differential mounted trigger wheel.

Issue

Commonly on older Toyota engines there was a dedicated speed sensor / cable that sent the vehicle speed information to the dash, and the dash then sent a digital electrical speed signal to the engine ECU. In this arrangement both automatic and manual transmission were fitted with the dedicated speed sensor.

In 2JZ-GTE VVTi (i.e. JZS161 and JZA80) the arrangement of the speed sensor, engine ECU speed input and the dash speed input are different. There are also difference between the different models and transmissions detailed below.

JZS161 Aristo Automatic Transmission

Note: JZS161 Aristo were only available with automatic transmissions.

Engine ECU: The engine ECU receives the vehicle speed from a 2 wire speed sensor what is triggered from a 12 toothed trigger wheel mounted on the gearbox output shaft. Once the automatic transmission is removed this speed sensor is also removed.

Dash: In JZS161 there is no dedicated speed sensor for the dash. The dash receives the vehicle speed via serial data from the engine ECU via the Multiplex bus.

JZA80 Supra Manual Transmission

Engine ECU: The engine ECU receives the vehicle speed via an electrical signal from the dash.

Dash: In JZA80 with manual transmission there is a dedicated speed sensor for the dash. The dash receives the vehicle speed via this sensor and also transmits it to the engine ECU via a digital signal.

JZA80 Supra Automatic Transmission

Dash: In JZA80 with automatic transmission there is no dedicated speed sensor for the dash. The dash receives the vehicle speed via a digital output from the engine ECU. It can be seen that once the automatic transmission and it's speed sensor is removed the engine ECU will be unable to send the vehicle speed to the dash.

Diff Mounted Trigger Wheel Drawings

One solution to the problem raised by the removal of the automatic transmission and as a result the effective removal of the dash speed sensor is to mount a trigger wheel to the tailshaft / rear differential input flange with the automatic transmission 2 wire sensor mounted to be triggered by the newly installed trigger wheel.

The trigger wheel should have 12 teeth (the same as the original automatic transmission trigger), however if items such as the wheel / tyre size or differential ratio have been changed then it maybe possible to account for these changes by modifying the number of teeth on the trigger wheel.

The following spreadsheet maybe helpful in calculating this,

20131203 Toyota A Series Diff Mounted Trigger Wheel.xlsx

Below are some drawings and images that show this solution.