Ron's Blog

What’s so COOL – Ford Ranger and BT50 Transmissions …

not much until extra transmission cooling is added!


After servicing many Ford Ranger / BT50 transmissions and seeing the destruction caused by towing (overheating) we had no choice but to do some investigation to find out why …

The first step was to fit a cooler to the Ron Hill Ute – ROY the Ranger we call him! He is the standard 6 speed Ranger and the Dual Heavy Duty Transmission Oil Cooler Kit was fitted – Ford Ranger PX Series 1 and 2 6R80 6 Speed Auto. Since it was essential to measure the temperature of the transmission oil, a scan gauge was connected. Roy was then driven from Coolum to Brisbane airport with 3 people in the car and without any load or towing.

After monitoring the display temperature for over an hour it was determined that the average transmission temperature was surprisingly 95 degrees celcius 

We were surprised that the temperature ran so high considering that Roy is still a new vehicle with only 20,000km on the dash and was driven without a load. Armed with this information of the extremely high constant running temperature and the fact that the manufacturer has set the cooling thermostat in the system to kick in at around 100 degrees celcius, highlights that the Ford Rangers and BT50s are running at higher than favourable temperatures for long periods of time. This is not ideal for our Australian climate.

To resolve the problem of the transmission oil temperature, a cooler flow control valve (upgrade) was also fitted to the valve body and the transmission was serviced. It makes sense to complete a service during fitting since there is no choice but to drain the transmission oil during this process.

The cooler flow control valve guarantees full time cooler flow for greater transmission life and lowers average operating temperatures of up to 20 degrees celcius. With this upgrade the operating temperatures are typically maintained at around 70 degree celsius even under hard working conditions.


  • Full time cooler flow ensuring a much lower operating fluid temperature
  • Built in high-pressure safety by-pass valve allowing unrestricted lube to the gear train
  • Immediate and accurate fluid level check without the need for a warm up cycle

Roy was then driven after fitting the cooler flow control valve to Brisbane again, this time to the 4WD show at Brisbane Show Grounds and this gave the opportunity to monitor the expected drop in transmission temperature. The transmission temperature did not exceed 70 degrees celsius!

 Happy days! Roy just saved $$$ in transmission repairs and doubled the life of his transmission! 

After road testing and monitoring the temperature gauge it is determined that to reduce the running temperature of the transmission oil these steps are required:

    • Fit a double core transmission cooler
    • Fit a cooler control valve – the valve body assemble is removed and the upgraded cooler control valved is fitted
    • Service the transmission – replace the oil, filter and gaskets
    • Perform transmission control module operation resets

The rule of thumb is that every 20 degree celsius drop in running temperature doubles the life of your transmission.

Before our research we were fitting coolers as a first step. We now recommend the cooler control valve upgrade with the fitting of the cooler to further reduce the running temperature of the transmission oil.