TCC Controller
automatic transmission ZF model
4HP24
General information
The 4HP24
automatic transmission has a built in lock up clutch
for the torque converter which eliminates the slip once engaged. The factory
design is that it works only in 4th gear and above roughly 100km/h.
This means, in all driving situations where this speed is not reached like city
and highway driving the torque converter is wasting expensive energy all the
time due to the slippage.
The extra
control unit takes over the control of the TCC (Torque Convert Clutch) and engages it already at the
much lower speed of 40km/h. It also engages the TCC gradually and not with a
“kick” like the factory EGS does it. This guarantees a much smoother operation
and of course puts much less stress on all mechanical components.
Once the speed
decreases below 40km/h the TCC will open immediately.
Installation of the internal TCC
control box
REQUIRED TOOLS:
The TCC
controller needs five electrical connections:
First Step
Locate the EGS
(Elektronische
Getriebe Steuerung = Automatic
Transmission ECU) on the inner right rear wheel arche inside the trunk.
Second Step
Unscrew the
10mm nuts which hold the EGS in place and the single 10mm nut connecting the
ground wire to the chassis.
Third Step
Disconnect the
EGS from the main connector (X8500) by flipping the silver handle upwards and
then removing the connector from the EGS. Take out the EGS.
Forth Step
Open the EGS. Using a screwdriver
the metal latches can be bent and the cover removed. You can now see the PCB
side of the X8500 connector as well as the numbers on the individual
connectors.
This drawing shows the connector
side of X8500 which goes on to the EGS unit.
The cables are on the opposite side.
Fifth Step
Connect the TCC
control box wires with the X8500 connector according to the below table.
All wires can
be soldered directly to the X8500 pins with a very fine soldering iron tip.
Last Step
Close the EGS
and reconnect it. After that just enjoy your increased gas mileage.
Options
If you want to make the TCC control box switchable run the brown wire
(ground) via a on/off switch.
For an optical control an LED (not a normal 12V lamp!!!) can be
connected parallel to PIN 35 (+12V) and PIN 25 (ground if TCC is in operation. This
of course requires, that you run a 4 wire cable out of
the EGS to your car’s interior.
Below pictures show as a sample the setup in my own 850.