Ford 10-Speed Transmission Cooling: Heat Exchangers, Control Valves & Basic Diagnostics

In case any of you have dealt with Ford 10-speed overheating issues, the powertrain cooling systems are worth knowing a bit about. These models still have radiators with typical functions like earlier vehicles, but like all things, technology has progressed over time with electronic components such as network bus systems, sensors and controllers/modules to improve function. That brings us to the single-most sought-after improvement for manufacturers: reducing the dirty emissions output during the first 5 minutes of a cold vehicle startup. A vehicle produces less emissions the quicker a powertrain can achieve operating temperature, and even a 20–30 second reduction in startup time is valuable when considering millions of vehicles have cold starts daily.

These specialty processes in the patent world are called active warm-up (AWU) and active transmission warm-up (ATWU). Vehicle manufacturers receive carbon reduction credits from the EPA for the use of these processes. AWU vehicles’ systems will use components such as integrated exhaust manifolds to capture hot exhaust thermal energy and other items such as high- and low-limit thermostats, grill shudders, heat exchangers, oil-to-air coolers, thermal bypass valves and solenoid-operated coolant control valves to further reduce emissions.

You might wonder how the transmission is a part of an emissions process, but a large part of the overall vehicle components participate in emissions, including specially formulated synthetic lubricants and coolants. Ford Motorcraft^® MERCON^® ULV (WSS-M2C949-A) is used in Ford 10-speeds. “ULV” stands for ultra-low viscosity, and this type of ATF is formulated to give certain properties necessary for the proper function of these units. These qualities include smoothness of shifting under a wide range of throttle conditions and temperatures as well as preventing problems such as unwanted clutch drag and bind-ups.

Two Basic Types of Transmission Cooling Systems

The Ford 10-speed cooling system’s main objective is to keep transmission temperature within +/-10°F (+/-12°C) of the engine temperature. There are two basic types of transmission cooling systems in Ford trucks with the 10R80, for example.

The first type has a large heat exchanger located at the transmission or frame rail. It will have engine coolant, radiator coolant and transmission fluid flowing in separate chambers to the heat exchanger. A solenoid-operated coolant control valve will control the transmission temperature by allowing either engine coolant to the heat exchanger to bring temperature up or by allowing radiator coolant by default (with no electrical solenoid activation into heat exchanger) to cool transmission fluid.

The second type will have a smaller heat exchanger and an oil-to-air, separate transmission cooler. It will have both a coolant control valve and a bypass valve integral to the heat exchanger. The coolant control valve allows engine coolant to flow through the heat exchanger to warm the transmission during initial startup, and then the bypass valve takes over by either sending fluid back to the transmission to warm the unit or to the cooler to cool the transmission.

Note: Some 10R80 valve bodies had a thermal bypass valve for cooler flow, and now in most valve bodies, the thermal valve element has been removed from the valve body bypass.

Solenoid-operated Coolant Control Valve Functionality

This coolant control valve deserves special mention as it has a history of failure. Methods of physical examination are outlined (Figures 1 & 2).

Figure 1 – Solenoid-operated Coolant Control Valve Functionality

Figure 2 – Solenoid-operated Coolant Control Valve Assembly

First, check the level and condition of coolant levels, engine oil and transmission fluid. Typically, these checks require the truck to be at operating temperatures 212°F (100°C) for accuracy, but follow Ford service manual instructions closely as there could be variable requirements. It is also a clever idea to ask the owner of the truck about previously performed maintenance.

It is important to refer to service manual data and become familiar with the exact cooling system and the components you are working on. Pay close attention to scanner data about both engine and transmission temperature. If the engine is overheating, that needs addressing first. Remember that the transmission will not typically cause the engine to overheat, but if the engine is overheating, it can cause the transmission to overheat. These engines are known for thermostat failures.

Depending on the condition of the problem, you might be able to set up a test condition to evaluate the truck in the bay with a fan blowing air into the front grill area and power braking the truck. Your best tools are an infrared gun with a minimum of 12:1 optics, adjustable emissivity and a laser pointer. A portable thermal imaging camera is a great tool as well, but remember that no matter which tool is used, it must be able to get in tight spaces on these trucks for testing.

Note: Excess wear at the TCC regulator valve bore and worn OE parts allow secondary line and TCC signal pressures to exhaust, resulting in loss of converter feed pressure and overheated fluid. Sonnax offers drop-in TCC priority valve kit 105740-03K and oversized version 105740-22K to restore hydraulic control and renew TCC performance. The drop-in kit is included in Sonnax Zip Kit^® 10L80-G1-10R80-ZIP.

Thanks to William Empke at Atlas Transmission for information related to the control valve. Enjoy!

Jim Mobley is a Sonnax technical communication specialist. He is a member of the Sonnax TASC Force (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax Transmission Company technicians.