Speedometer:
We have a whole page on the Ranger's speedometer HERE. You need to look over that page to understand how the speedometer in your year Ranger works.
The speedometer may very well be one of your toughest obstacles. If you have a 1995-2000 Ranger you should try and get a 5.0L EFI setup that's going to match the speedometer setup your Ranger has. This will simplify things for you.
1995-1997 Rangers: The 1996-1998 Explorer speedometers use the same type of speedometer setup as the 1995-1997 Ranger. It has a VSS located near the rear section of the transmission/transfer case that gets input from a gear driven speed sensor on the output shaft.
The Vehicle Speed Sensor (VSS) is a small signal generator that is turned by a gear inside the transmission assembly. The Vehicle Speed Sensor produces 8 pulse per rotation which a stock computer assumes 8000 pulses per mile. The Vehicle Speed Sensor (VSS) is a variable reluctance sensor that generates a waveform with a frequency that is proportional to vehicle road speed. When the vehicle is moving slowly, the sensor produces a low frequency signal. As the vehicle speed increases, the sensor produces a higher frequency signal.
1998-2000 Rangers: 1999-2001 Explorer uses the same type of speedometer system as the 1998-2000 Ranger - no modifications needed. The 1998-2000 Rangers are not equipped with a VSS (Vehicle Speed Sensor). The PCM (Powertrain Control Module) receives vehicle speed information from the antilock brake system rear wheel speed sensor. The raw signal from the ABS/VSS sensor on the rear axle goes directly to the Explorer 4WABS module where the signal is corrected for tire diameter. Then the corrected signal is sent to the PCM, speed control, cluster, etc. In this system, the PCM is an end user of the corrected VSS signal.
2001-Newer Rangers: The problem comes when you drop the 5.0L Explorer engine in to a 2001 and newer Ranger. Starting in 2001, the Ranger gets its raw speed signal from the OSS (Output Shaft Speed) sensor on the transmission/transfer case. The OSS sensor is a magnetic pickup that provides transmission output shaft rotation speed information to the PCM (Powertrain Control Module) where it is corrected for tire diameter and axle ratio. The PCM uses the OSS sensor signal to help determine EPC (Electronic Pressure Control) pressure, shift scheduling and TCC (Torque Converter Clutch) operation. The PCM generates a 0~12V square wave. This frequency of the square wave is corrected to provide a standard 8000 pulses/mile using multipliers flashed into the PCM for axle ratio and tire diameter. It is sent to the speed control and the cluster. In this system the PCM is the correction and distribution point for the VSS signal.
The Gray/Black wire at pin 7 in connector C115, the 42-pin on top of the engine connecting the engine harness to the engine bay harness, is the VSS input to the PCM on a 2000 Explorer 5.0L.
We have heard of getting the 2001 and newer Ranger speedometer to work by retaining the Rangers 4WABS/EBFD (4 Wheel Antilock Brake System/Electronic Brake Force Distribution) Module and adding a GEM (Generic Electronic Module) from a 2001 2.5L. Both are driven in parallel by the rear axle ABS sensor. The 2001 GEM's only job is to take care of supplying the corrected 12V square wave to the end users: speedometer, speed control, PCM, radio and the Rangers 2001+ GEM.