Arduino Tiptronic Shifter

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Project Description

I have very limited knowledge of programming and Im new to the Arduino platform but it seems to be the best option for my project. I want to make a tiptronic shifter to control the auto transmission in my jeep. The stock transmission control unit will still be used and this would act as a piggyback unit. I already started this project with someone else but it was never finished. I will attach the code already written in case it helps.

It would be able to pick up from the automatic transmission's existing gear for when you switch between auto and manual mode while driving. (program starts in Auto) It would use a 2 way momentary toggle switch to up shift or down shift. There would be a second toggle switch to manually lock the torque converter (when switch not engaged, lock up signal would pass through from the stock transmission control unit) and a momentary push button to switch from auto to manual shifting mode then back. Attempting a shift while in auto mode would also force the controller into manual mode. While the torque converter was manually locked, it would need to temporarily disengage during a shift. There would also be a LCD display to show what gear the trans is in, whether the torque converter was locked or unlocked, and whether the controller was in auto or manual mode.

The trans operates on 3 12v solenoids. 2 of the solenoids control 1st through 4th gear like this.

#1 on, #2 off, 1st gear

#1 on, #2 on, 2nd gear

#1 off, #2 on, 3rd gear

#1 off, #2 off, 4th gear

The 3rd solenoid is for the torque converter lock up.

I also need to trick the TCM into thinking it is controlling the transmission so that it doesnt set off a check engine light and go into limp mode. This would include a program to read a Variable Reluctant Sensor input and then output a signal to mimic a rear sensor in the gear the TCM is in.

I believe the logic would look something like this.

Front Speed sensor input = frequency

Rear Speed sensor output = calculated frequency per gear divided 4 as the input sensor is 16 pulses per rev and output is 4 pulses per rev.

If sol1 input=1 and sol2 input=0 (1st gear) then rear speed sensor = front speed sensor*.3571 (1st gear ratio) /4

If sol1 input=1 and sol2 input=1 (2nd gear) then rear speed sensor = front speed sensor*.6535 (2nd gear ratio) /4

If sol1 input=0 and sol2 input=1 (3rd gear) then rear speed sensor = front speed sensor*1 (3rd gear ratio) /4

If sol1 input=0 and sol2 input=0 (4th gear) then rear speed sensor = front speed sensor*[url removed, login to view] (4th gear ratio) /4

So there would be (3) 12v inputs from the TCM for solenoids 1-3, inputs for controlling the unit; 2 momentary for up shift and down shift, 1 momentary for switching between auto and manual, and 1 non momentary or tcc manual lock up or torque converter auto lock up.


Front Speed Sensor Input from Transmission VR Sensor

Sol 1 Input from TCM

Sol 2 Input from TCM

Sol 3 Input from TCM

Up Shift from Momentary Switch

Down Shift from Momentary Switch

Auto Switch from Momentary Switch

TCC Lock from On/Off Switch


LCD Din Output

LCD D/C Ouput

LCD CS Output

LCD RST Output

Rear Sensor Output to TCM

Sol 1 Output to Relay Shield to Transmission Solenoid

Sol 2 Output to Relay Shield to Transmission Solenoid

Sol 3 Output to Relay Shield to Transmission Solenoid

Below is the proposed list of hardware.

Main Board (will except 12v inputs)

[url removed, login to view]

To drive the Solenoid Outputs

[url removed, login to view]

To condition the Variable Reluctant Sensor Input Signal

[url removed, login to view]

LCD DIsplay (open for other screen suggestions that wont overload us on pins

[url removed, login to view]

Let me know what you think and if you have any questions. I would love to work on this project with you. You can message me at froehlichsuspension at [url removed, login to view]

Kris Froehlich

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