I have a set of 3.73 gears I want to put in the CLK, but if you change the gear ratio you need to reprogram the Transmission Control Unit (TCU) so it knows how to perform its speed calculations. I could have a tuner modify my stock
TCU, but I decided to take this opportunity to replace the factory TCU with a TCM2800 aftermarket controller by Powertrain Control Solutions. I got the controller from Sound German Automotive in Bellevue, Washington. Russell at SGA is a 722.6/NAG1 transmission guru who knows everything you could imagine about these transmissions.
Installing the controller was a breeze. The controller comes with a harness that has the transmission connector pre-terminated and ready to install. The only other connections I need for my current setup are the CAN bus, switched and unswitched power, and a ground. The kit also includes a tone ring and inductive pickup that you can mount to the tailshaft of the transmission to acquire a vehicle speed signal, but for now I’m getting that value over the CAN bus.
There are other provisions in the harness for connecting a PCS display unit, or for getting signals for RPM, TPS, and VSS directly from their sources. I will use those instead of the CAN signal when I eventually replace the OEM ECU with the Holley Dominator.
I took the car for a drive and it shifts nice and firm, but not jarring. Virtually everything is tuneable, from shift points and quality to torque converter lockup. I will work with Russell to fine-tune the values and take it to the track next weekend to see how it performs in the 1/4 mile under WOT. Weather permitting, I should be able to run the first 12 second pass in this car!