Zf 6 Speed Best External Trans Cooler?

[GeorgeGhia]

Hi jules_1972,

As you can't go to Ford Forum here's copy of a post from my stream, includes extract from my Ford BF workshop manual.

It has taken me a while to take in the significance of the call from ZF, I had emailed them about 2 weeks ago and received confirmation of my query, but was beginning to think that was all I would get, but Yes, the information received from the ZF tech is invaluable and I now feel we can be totally confident that the decision to remove the Ford heat exchanger and install an air/cooler was the right one. No risk of Milkshake and longer transmission/fluid life.

My first thought was to share the info with my fellow forum members, and then armed with the new info I read through my Ford workshop manual transmission section again. I now have a much better understanding of how the ZF6 operates and have since done some more monitoring of my transmission temp and functions. 
I felt that the most important pieces of info to come from ZF was the minimum optimum operating temp of 30C for the ZF6, that ZF6 has a designed in strategy to bring the trans fluid up to that temp from a cold start, that ZF test run the ZF6 as low as minus 20C, and it is beneficial to the life of the trans and fluid to run at lower temps. As I have always said, the ZF6 is very smart.
It is obviously desirable that we run our trans at optimum operating efficiency and so to this end it would be good to have it running at a minimum of 30C sooner rather than later. The ZF6 has a designed in strategy for this and we probably don't need to do anything, but, as I do a lot of short runs I thought I would try different strategies to help warm up the trans from cold starts, also thought our friends in colder climes would be interested to know.

Here's the results of recent test runs on cooler MELBOURNE mornings.

Strategy1:A/C on auto 21.5C, Manual shift for first 5mins then Auto.
Ambient temp 16C, Start up engine temp 44C, trans temp 19C, 
after 5mins, engine temp 80C, trans temp 30C.
after 10mins, engine temp 85-92C, trans temp 40-43C.

Strategy2:A/C on auto 21.5C, Auto shift.
Ambient temp 19C, Start up engine temp 43C, trans temp 21C,
after 5mins, engine temp 85C, trans temp 30C.
after 10mins, engine temp 85-92C, trans temp 39-42C.

Not a lot in it really, think I will leave to the trans to look after itself,
smarter than me I think.

Here's an extract from my Ford BF Workshop Manual re the ZF6 transmission which explains among other things how the trans temp is monitored and regulated.

DESCRIPTION AND OPERATION

Transmission Electronic System

The transmission control module (TCM) and its input/output network control the following transmission operations:

Shift timing.

Line pressure (shift feel).

Torque converter clutch.

In addition, the TCM receives input signals from certain transmission-related sensors and switches. The TCMalso uses these signals when determining transmission operating strategy.

Using all of these input signals, the TCM can determine when the time and conditions are right for a shift, or when to apply or release the torque converter clutch. It will also determine the pressure needed to optimize shift feel. To accomplish this, the TCM uses six pressure control solenoids and one shift solenoid to control transmission operation.

The following provides a brief description of each of the sensors and actuators used to control transmission operation.

TCM

CAUTION: Should you be required to reprogram the TCM the following criteria must be observed:-

The transmission fluid temperature must be below 80°C

Park (P) or Neutral (N) selected

The handbrake firmly applied

The TCM for the transmission is mounted on top of the main control valve body. The control module for the transmission has been designed to operate correctly in the environment in which the TCM is located.

The transmission control module is activated and deactivated by the ignition supply and is connected to the transmission link harness by a 16-way connector.

The TCM controls the operation of the transmission. The TCM processes information received in both analogue and digital form such as:

Transmission input speed

Output speed

Throttle pedal position 

Gear selector position 

Engine torque

Engine speed 

Transmission fluid temperature

Brake pedal status

Engine oil temperature 

Coolant temperature

ABS wheel speed

This information is then used by the TCM to decide which shift pattern to select and for shift energy management. Electro-hydraulic solenoid valves and pressure regulators control the transmission gear changes.

Five pressure regulators and one solenoid valve are used to control direct transmission fluid flow to select internal clutches and control the fluid pressure at the clutch. A separate pressure regulator is used exclusively for torque converter clutch control.

The TCM monitors all TCM inputs and outputs to confirm correct system operation. If a fault occurs the TCMis able to perform default action and inform the driver of the problem, this is by the instrument cluster message centre.

Solenoids

The hydraulic module contains one solenoid valve. The solenoid valve is actuated by the TCM and has two positions of open or closed, it is used to switch the position valve.

There are six electronic pressure control valves, these convert an electric current into a proportional hydraulic pressure. They are energized by the TCM and actuate the valves belonging to the relevant switching elements.

Controller Area Network (CAN) Interface

For the TCM to be able to perform shift point and shift quality management a number of external signals are required. For shift point management alone the TCM requires output speed sensor, throttle pedal position, brake pedal status and gear selector position. The controller area network (CAN) bus is used to share information between control modules. The TCM obtains most of its required data over the CAN bus from the electronic engine controls, Sequential Sport Shifter and ABS, Instruments pack and diagnostic tools.

Brake Pedal Position (BPP) Switch

The brake pedal position (BPP) switch tells the TCM when the brakes are applied, and disengages the torque converter clutch. The BPP switch closes when the brakes are applied and opens when they are released. The BPP is also used to disengage the brake shift interlock and stops gradient calculations.

Engine Coolant Temperature (ECT) Sensor

The engine coolant temperature (ECT) sensor detects engine coolant temperature and supplies the information to the TCM. The ECT sensor is used to control the torque converter clutch (TCC) operation.

Accelerator Pedal Position (APP) Sensor

The accelerator pedal position (APP) sensor is a potentiometer mounted on the accelerator pedal. The APP sensor detects the position of the accelerator pedal and sends this information to the electronic control module (ECM). The APP sensor is used for shift scheduling and TCC lock-up.

Input Shaft Speed (ISS) Sensor

The input shaft speed (ISS) sensor is a Hall Effect type sensor.

The ISS sensor is mounted internally on the transmission and is located on the TCM and main control valve body unit.

Output Shaft Speed (OSS) Sensor

The output shaft speed (OSS) sensor is a Hall Effect type sensor.

The OSS sensor is mounted internally on the transmission and is located on the TCM and main control valve body unit and is used for shift scheduling.

Transmission Fluid Temperature (TFT) Sensor

The TCM utilizes one transmission fluid temperature sensor located on the main control valve body. The TCMuses the sensor input to activate various shift strategies. The sensor is in the form of a temperature dependent resistor.

The temperature sensor performs plausibility checks on each sensor reading. Obviously, the transmission oil temperature should not jump in value excessively between sensor readings. If the inputs from the temperature sensor are outside the working range it possible that the sensor is short or open circuit.

Position sensor

The TCM uses the position of this switch housed on the TCM and main control valve body, to determine the selected gear range on the Automatic side of the selector lever. 

The selector lever is connected to the transmission by a cable, which operates the transmission selector shaft between positions Park, Reverse, Neutral and Drive. The TCM detects the driver’s choice of manual range selection (+ or -) by means of a 3-bit code generated by the printed circuit board (PCB) housed within the selector assembly. This 3-bit code is then transformed in to a CAN message by the PCB and transmitted on to the CAN bus where it is detected by the TCM.

The TCM uses this information to generate the CAN message "Gear Position Selected", which must not be confused with the similar message "Gear Position Actual" indicating the current mechanical gear ratio activated by the TCM.

Movement of the lever between Park, Reverse, Neutral and Drive manually controls the flow of transmission fluid, the TCM having control of the forward gear selected in Drive. Additional movement of the lever to 5, 4, 3 and 2 positions does not manually modify the fluid flow, the TCM detects these positions, and controls the gear selected electronically.

Sport mode shifter position

The sport mode:

Allows the driver to select or de-select the automatic transmission sport mode.

Allows the automatic transmission to operate normally when the sport mode is selected, but under acceleration the gear shift points are extended to make full use of the engine’s power reserves.

Allows the driver to drive the vehicle in the "D" position with the full automatic transmission shift or manually shift the gears through 2nd, 3rd, 4th, 5th and 6th gear by using the + and - positions.

"S" is illuminated when Sport mode is selected.

Communicates with the TCM through the CAN network to show the sport mode switch status.

TCM Monitoring Functions

As explained above the TCM monitors all input and outputs to identify possible failures. If a fault is detected the TCM takes the appropriate action to ensure the transmission enters a safe mode of operation, without sacrificing transmission durability or driver safety.

Supply Monitoring

If the battery voltage is either too great or too low, the TCM will detect a fault condition. For the TCM to be able to identify this fault the engine must be running and the transmission fluid temperature sensor must be functioning correctly

DESCRIPTION AND OPERATION (Continued)

monitoring function evaluates the voltage characteristics during the switch on process checking for the above faults.

All solenoid outputs are fully protected. The processor and the appropriate fail-safe action taken can quickly identify open and short circuit faults.

Sensor Supply Monitoring

The sensor supply voltage is a stabilized supply. This supply is monitored by the micro-processor by an Analogue to Digital Converter (ADC). If the voltage is out of the valid tolerance a raise a diagnostic trouble code (DTC) is set and the appropriate fail-safe action is performed.

Electronically Erasable Program Read Only Memory (EEPROM) Monitoring

CAUTION: Should you be required to reprogram the TCM the following criteria must be observed:-

The transmission fluid temperature must be below 80°C

Park (P) or Neutral (N) selected

The handbrake firmly applied

To diagnose errors with the electronically erasable program read only memory (EEPROM) the TCM calculates 4 checksums continuously: If the processor identifies discrepancies in any of the four checksums the TCMwill engage mechanical limp-home mode.

The TCM can diagnose errors within the EEPROM. Diagnosis is only performed during TCM initialization. There is no fail-safe mechanism associated with this function as the EEPROM is mainly used for the storage of fault codes and transmission calibration adaptations. If a fault occurs the TCM is able to perform default action and inform the driver of the problem, this is by the instrument cluster message centre.

Watchdog Monitoring

The watchdog monitoring function has two functions. Firstly it checks that it is possible to inhibit output control by the activation of the solenoid supply transistor. Secondly the watchdog checks that the safety circuit is functioning correctly.

During initialization the watchdog checks that it is possible to inhibit control of the pressure regulator and solenoid valves by switching the solenoid supply transistor. There is a fault if activation of the solenoids cannot be inhibited by the watchdog (NB. The supply to the solenoids can still be inhibited by the high side switch responsible for control of each solenoid I.e. One safety path is lost).

Monitoring the Substrate Temperature Sensor

The TCM is situated within the transmission on the valve body. As the TCM controls a number of high power solenoids and is surrounded by ATF, the TCM

can obviously get very hot. If the temperature of the hardware rises above a pre-determined level the TCMwill be shut down. Prior to the TCM shutting down the TCM will log a fault code, during shutdown the transmission will enter mechanical limp-home mode. Monitoring of the substrate temperature is performed by a temperature dependent resistor mounted on the processor.

Plausibility Checking

The TCM detects a fault if an excessive voltage jump is identified between any two consecutive measurements. Also, with the engine started from cold the transmission fluid temperature will start to rise. Therefore the substrate or fluid temperature will also start to rise because the TCM is surrounded by transmission fluid. If the engine and output shaft speed is higher than a set threshold for a predetermined length of time without the substrate temperature rising above a set threshold a fault will be detected.

Pressure Regulator/Solenoid Monitoring

Each pressure regulator and solenoid is monitored for open circuits and short circuits. The TCM also checks that the current being delivered to each solenoid valve or pressure regulator is within valid limits. When each solenoid is being driven with minimum current the TCM checks that the current is not above a threshold value. If a solenoid is being driven with maximum current, it checks that the current is not below a valid threshold. If either of these two errors occur, a plausibility error is logged and the appropriate fail-safe action is performed.

Output Speed Monitor

It is possible for the TCM to diagnose electrical errors associated with the output speed sensor while the vehicle is stationary as well as moving. Plausibility monitoring is performed on the sensor output when the vehicle is moving.

Input Speed Monitor

It is possible for the TCM to diagnose electrical errors associated with the input shaft speed sensor while the vehicle is stationary as well as moving. Plausibility monitoring is performed on the sensor output when the vehicle is moving.

Transmission Fluid Temperature Sensor Monitoring

The TCM monitors for faults associated with the transmission fluid temperature sensor in the following ways:

1. Open and short circuit fault detection.

2. The temperature cannot alter by more than a predefined differential between any two consecutive measurements.

3. The transmission fluid temperature must rise after the engine has been started provided that the fluid temperature was low enough to begin with (The vehicle must be driven and the diagnostic test condition met). 

Torque Converter Lock-up Control

The TCM controls how the torque converter clutch is engaged as a function of the accelerator pedal position, output speed, transmission fluid temperature, gear selected and shift program. Lock-up is possible in all forward gears, but usually it is restricted to fourth, fifth and sixth gears. To make use of the comfort enhancing effect of the torque converter, the converter clutch can be disengaged prior to a downshift or up-shift. The torque converter lock up clutch is always modulated to allow for controlled slip, to further improve the shift quality. 

"Let's eliminate the Milkshake"

Regards, George

[barnz]

I must have missed the pretends it didn't happen part? Pretty sure I was pretty open and honest about it? 

why so serious I didnt say you weren't...was just like cheats death, carry on anyway sort of metaphor

[julesk_1972]

Excellent info George, much appreciated!!!

I was not aware of the level of intelligence in the ZF6 operations.

Very impressive.

Thanks.

Sent from my HTC One_M8 using Tapatalk

[hjtrbo]

Just came across this thread today. I have had average to poor shift quality that I have ignored after changing ZF strategies from FG XR6T to FG F6 a few months back. I always though it maybe was something to do with my torque model that perhaps wasn't right for the F6 strategy. I just left it as is because I couldn't be bothered to try and fix it. The niggles were minor enough to warrant leaving it. Anyway......

Current set up: External cooler, trans temps always around 50 - 65degC. No thermal bypass valve on external cooler.

The other day I took it out for a proper hiding around some winding country roads, the first warm day of the year and got trans temp up to a peak of 80degC which was the highest it's been since the cooler install some 6 months ago.

The next day, shifts were on point. Done some digging in the ZF parameters and found evidence to support a claim that adaption starts at 70degC and ends at 95degC. 

[GeorgeGhia]

That is very interesting info, that would be set up for the heat exchanger temperature range I guess, can it be adjusted?, also interesting that the line below it says "Minimum temperature for activation is 20C'.

 

Where did you get the info from?

[hjtrbo]

@GeorgeGhia PCMTEC editor software

Edited 30/11/21 12:07 AM by hjtrbo