Installing a truspeed speedometer calibrator •  by Christo Slee


The Superlift TruSpeed Calibrator

IMPORTANT: These installation instructions are written for a 1995 US Spec 80 Series Land Cruiser. Please refer to your electrical manual for specific details on your truck. If you are not familiar with automotive wiring, or are not comfortable to install the unit, please take it to a professional shop. Incorrect wiring can leave your vehicle inoperable, or worse, you can fry the ECU.


Schematic Overview

DISCONNECT BATTERY BEFORE DOING ANY OF THE WIRING.

The TruSpeed is installed in-line with the speed signal wire coming from the speedo gear encoder on the transfer case. The easiest place to tap into this line is behind the glove box. Even then, the space is limited, but it can be done. 

The TruSpeed has two calibration settings and allows you to set the speed for two different sets of tires with the flick of a switch. The adjustments are done by turning a small screw on the side of the box. 

The TruSpeed unit has 4 wires on it:

BLACK - Ground
Red - +12V
Green - to the speedo gear encoder (transfer case side)
Yellow - to the ecu

The  black/red wires are tapped to a ignition +12v source and ground. The green/yellow wires are spliced in-line with the speed signal wire. We cut the harness to a suitable length to install, and use the excess to tap into the car harness. 

We chose to actually install the unit in the glove box, with sufficient wire on the harness to remove it from the glove box, do the tuning and then stick it back on the velcro pad. 


This image shows the TruSpeed installed in the glove box. The harness is split loomed and exits the glove box at the bottom through a grommet.


This image shows the harness exiting the bottom of the glove box. The harness is terminated in two 2-pin Molex connectors. The red/black and green/yellow wires are paired together.

Once the unit is installed into the glove box, the next step is to tap into the car harness. This is where you need your electrical manual. On page 163 of the 1995 Model Electrical Wiring Diagram manual ( the section on the Combination Meter (gauge cluster)) it shows a connector IH1. This is the connector that we are trying to locate. 


This shows the IH1 Connector



Pin 1 wire, cut and stripped

The speed signal wire on this plug is pin 1. A red wire with orange stripe. The pin-out of this connector is show on page 32 of the manual. Since the green wire needs to be connected to the speedo gear encoder side (transfer case) we need to know which side of the plug this is. 

The wiring manual also shows us that the male side of the plug is the side that comes from the combination meter (gauge cluster) and the female side is towards the transfer case. 

Unplug the male side of the harness from the main car harness. Now strip back the protective sleeve until you have about 2-3" of wires exposed. Cut the red/orange wire about 1" from the plug. Strip the ends and solder about 12" piece of the green wire (the excess that was cut off previously to the red/orange wire closest to the plug. 

Strip the other end of the red/orange wire and solder a similar piece of yellow wire to this red/orange wire. Cover with heat shrink. We also use zip ties to tie them together to serve as a strain relieve.


IH1 connector with green and yellow wires spliced in.

This takes care of the signal part. We now need a +12v ignition source. Pin 6 on the same connector (yellow wire) is a +12v source that supplies power to the vehicle speed sensor as well. We can just tap the red wire of the TruSpeed into this wire. Remove a small piece of insulation from this wire, solder the red wire onto it, and cover with electrical tape and a zip tie.  

Also install a black wire from a suitable ground point. Now pair the yellow/green wires together and the black/red wires together. 


IH1 connector with green/yellow wires installed with heat shrink and red +12 v wire spliced in.

We now install two Molex connectors on the other ends of these pairs of wires. The Molex connectors will plug into the wires coming from the TruSpeed unit. 

Split loom the cables, and plug the IH1 connector back to the harness. You can now connect the battery again.


Wire pairs with Molex connectors installed.

IMPORTANT: Before plugging the TruSpeed unit in, verify with the ignition on that you have +12 v on the red wire and the black is ground.

With the ignition off, you can now plug the TruSpeed unit in and take it for a test drive. Calibrate the unit as per the instructions supplied. 

It is also a good idea to make a little jumper plug that will jump the green/yellow pair of wires together. This will allow you to unplug the TruSpeed unit and restore the vehicle to stock if the unit fails. 

Details on purchasing a unit.