Six Ways from Sunday: Diagnosing ZF6 & Ford 6R60/80 TC-Related Drivability Concerns

When the scanner indicates operating temperature has been obtained and that the TCM is controlling the lockup solenoid, WK pressure should drop to between 0 and 2 psi (0 to .13 Bar). Zero pressure indicates full apply, and at 1.5 to 2 psi the TCM is allowing a slight slip rate to reduce noise, vibration and harshness (NVH). Note that these units do not use a continuous slip rate like we see in GM. In order to improve fuel economy, the ZF6 family often applies the converter clutch full-on and as early as possible, shortly after a 2-3 shift and in many instances just after completing the 1-2 shift.

How do you know if the converter is in partial slip or full lockup? Compare the TCC solenoid amperage to WK pressure. The TCC solenoid is a normally vented or normally open solenoid. As amperage increases, TCC apply increases and WK pressure drops. An effective way to check if the converter clutch is slipping is to monitor engine RPM and turbine or input RPM on the scanner. If WK pressure is zero, those two RPM sensors should match each other. Some tools retrieve data on “Torque Converter Amplification”; once the converter is fully applied and there is zero WK pressure, amplification should also be zero.

There are six general symptoms that stem from abnormal WK, and you’ll run into them every day of the work week. These are:

The first three are expected symptoms, but the last three may be a surprise to some technicians so we’ll look into those a bit further.

Harsh Shifts: The converter releases on a coast 2-1 downshift and some high-throttle, hard 3-2 events. WK pressure and the solenoid info in the scanner will indicate when it is released. If WK does not increase beyond 2 to 5 psi during 2-1 or forced 3-2, the shifts will occur on a locked clutch and feel harsh.

Flare Shifts: Typical converter strategy is full apply after the 2-3 shift and no TCC slip during shifts. Watch the solenoid signal with a scanner and monitor WK pressure. If WK is above zero when it should not be, that shift will feel like a flare as RPM spins up due to converter slip.

Rough Idle in Reverse: Is the rough idle only in Reverse? If yes, is WK low, such as 50 to 60 psi? If WK is low, then the converter clutch is not releasing properly due to a low pressure source or pressure loss. If WK is normal and the engine idles rough, then the converter lining is suspect. Before condemning the lining, verify the engine mounts are not blown. Then drive with the scanner and monitor slip under high-torque conditions. If WK is normal and the solenoid command is low, consider the converter.

If the WK pressure test is out of range or the cooler flow is incorrect, consider the following when troubleshooting:

As previously noted, line pressure is a priority, so bore wear at the main regulator valve (SYS.DR-V) will rob converter feed. Once at operating temperature, WK oil leaves the converter and returns to the valve body. At the valve body, converter internal pressure is controlled by the converter release regulator valve (WK-V), and the bypass clutch control valve (WD-V) acts as the switch. Fluid exiting the converter is controlled by a lubrication control valve (SCHM-V). The solenoid pressure regulator valve (DR.REO-V) supplies a regulated pressure to all solenoids. This includes the TCC solenoid, so if the solenoid regulator bore is worn, all solenoid output will either be too high or too low. Problems with any of these items will alter WK pressure. Vacuum test these valve bores, and if worn — as they commonly are — service them or obtain a remanufactured valve body.

The TCC solenoid (Figure 2) controls WK through the use of the TC valves noted above. This solenoid is known to wear out or become contaminated. In fact, all the regulating solenoids in these units have had issues. Mechanical rather than electrical failure is the common culprit of solenoid problems in the ZF6 family. These solenoids can be easily vacuum-tested to confirm failure.