Other Articles - October/November - 2020

Diagnosing the Erratic Shifting Ford’s 8F35/57

Ford’s 8F35 transmission might be years away from your shop, but knowing how do deal with some of the common complaints might help you gain an advantage over your competition.

Valve Body Issues

Some 2019 Edge/Nautilus/Transit Connect vehicles equipped with an 8F35 transmission may exhibit an illuminated malfunction indicator lamp (MIL) with diagnostic trouble code (DTC) P0766 and/or intermittent or delayed reverse engagement concerns.

This may be due to contamination in the valve body separator plate orifice. To correct the problem, remove and disassemble the valve body. Inspect, clean, and remove any debris from the separator plate orifice. (Figure 1) Replace or reinstall the parts. Clear the codes and retest the system for repair. That was easy!

Harsh Shift Reprograms

Some 2019 Edge/Nautilus vehicles equipped with an 8F57 transmission may exhibit a harsh upshift and downshift. They may also have harsh engagements from Park to Reverse, Park to Drive, or Reverse to Drive (with no DTCs present). The vehicle may also exhibit a 4th to 5th gear upshift flare.

This may be due to various powertrain control module (PCM) software parameters for harsh engagements when shifting from various shifter selector positions. Reprogram the PCM to repair these symptoms. That was easy, too.

Module Configuration Issues

Codes U2100 and U2101 indicate that a module is not configured properly. Check the repair history for any module replacement and verify all adaptive learning and training procedures were completed. If you still have DTCs U2100 and/or U2101 then check to see if your scan tool supports the “Integrated Diagnostic System” (IDS). If so, go to IDS > Toolbox > Module Programming > As-Built > select the module.

When asked, “Were you sent here to obtain part numbers from another procedure?” answer “NO.” From there, you can configure the module. If the vehicle is supported by the Ford Diagnosis and Repair System (FDRS), run the Module Configuration Application. This takes a little patience, but you’ll get the hang of it.

Fluid Leaks

Some 2019 Focus/Transit Connect/ Edge/Nautilus vehicles equipped with 8F35 transmission may have fluid leaks from the transmission axle shaft seal. This condition may be caused by an excessive amount of internal seal grease (dark brown) that was applied during the manufacturing of the axle seals. Clean the area thoroughly. If not, replace the seal (we tried for an easy one, here).

Shift Points

At times the 8F transmissions may skip gears when the vehicle starts from a complete stop. But during quick acceleration, it’ll use more of the available gears, and feel like it’s “speed shifting.” All of this is normal. It’s designed to keep the engine RPM closer to the horsepower peak for the best performance and fuel economy.

But if you think there’s a problem, you can always reset the shift points. Here’s how:

Bring the engine and transmission up to normal temperature. From a stop, accelerate the vehicle to 50 mph with the shifts occurring at approximately 2,000 RPM. Stay in 8th gear for at least 30 seconds or until the TCC applies. Repeat this two times.

Then, from a stop, accelerate the vehicle to 50 MPH with the shift occurring at 3,000 RPM. Stay in 8th gear for at least 30 seconds or until the TCC applies. Repeat this two times, as well.

If the transmission fails to upshift or downshift in a normal manner, you’ll need to further the diagnosis. Refer to the shift speed chart, you’ll be driving at light throttle during this test.

Transmission System Operation and Component Description

The PCM and its input/output network controls the shift timing, and the line pressure or shift feel. The following sensors are inputs are pretty standard, compared to other vehicles you’ve worked on, but use it as your check list:

Transmission Fluid Temperature Sensor (TFT): The TFT is located on the Valve body, the resistance value of the sensor varies with temperature change. The PCM uses this signal to determine whether cold start shifts are necessary. These delayed longer shifts help warm the vehicle to normal operating temperature faster.

Transmission Range Sensor (TR): The Park by wire duel range sensor indicates the state of park system. The cable shift duel range sensor determines the customer selected shifter position.

Turbine Shaft and Intermediate Shaft Speed sensor (TSS/ISSA): The TSS/ISSA sensors are Hall Effect type sensors that provide a signal to the PCM. The TSS is triggered by the rotation of the B clutch cylinder. The ISSA reads off of the sun gear and is part of the TSS sensor. The TSS/ISSA information is compared to engine RPM to determine Ratio and performance. It is also compared to the Output Speed Sensor to determine shift quality and clutch performance.

Output Speed Sensor (OSS): The OSS is also a Hall Effect sensor that provides an OSS signal to the PCM. The OSS reads off of the park gear and is used for shift quality.

Transmission Fluid Pressure Sensor (TFP): The TFP is used to help diagnose clutch A (TFP A) and clutch B (TFP B) for non-electrical faults such as stuck valves or a mechanically faulty solenoid. These pressure readings are used to monitor the status of specific clutch systems during operation.

Engine Speed: Directly affects shift scheduling, TCC control, line pressure and transmission diagnostics. Indirectly affects shift pressure control.

Engine torque estimate: Directly affects shift pressure control, TCC control and transmission diagnostics. Indirectly affects shift and TCC scheduling.

Accelerator Pedal Position Sensor: Directly affects shift scheduling, TCC scheduling and transmission diagnostics. Indirectly affects TCC control and shift control.

Commanded engine torque: Directly affects shift scheduling, TCC scheduling and transmission diagnostics. Indirectly affects shift control.

Brake Pedal Position Sensor: Directly affects shift and TCC scheduling.

As transmissions evolve, so do we. Keep learning about the newer transmission as they come out; one day, a new customer will come into your shop with a new vehicle. Be the first shop on the block to have the answers to these simple problems.