Thread: Paddles - manual shift of Auto

Crazy idea, but thinking about a new project, has anyone tried, or how hard would it be to be able to attach some electrical override system whereby we could manual change the auto box like those modern cars ??!!

If by shifting the lever we are telling the box which gear to be in, then it must be possible to link into the wires going to the CANBUS or somewhere similar so we can override and if so, then we can start talking paddles or some other silly idea ?

Has anyone considered this, how hard would it be ?

Reason for the post is that I have been driving a Volvo XC90 diesel for past 6 weeks, and as so often happens with Auto's they often seem designed with petrol and diesel engines in mind, hence they are a compromise and I find I can make the car so much happier and a pleasanter and smoother drive when I change manually, changing up gears before a bend and always being in the right gear to pull away, not waiting for a laboured kick down which is always too late and after you needed the torque.

What a great addition to a TD5 it would be

Originally Posted by Sneaky

This auto is half mechanical shifting and half electronic
The mechanical side selects between park , neutral , reverse and forwards.
It would be very easy to manually control which forward gear the auto is in with a relatively simple circuit - but I am not sure what the computer would do if it lost all control of the gearbox though.
If you disconnect the MV1 and MV2 from the computer and switch the solenoids yourself its easy to control it - you can even control the TC lockup with MV3.
MV1 is pin 30 of TCU
MV2 is pin 33 of TCU
MV3 is pin 32 of TCU
You will have to put some resistors from the disconnected TCU pins to 12V so the TCU still thinks its connected to the solenoids - MV1 and 2 needs 26 Ohms and MV3 needs 32 Ohms.

1st gear MV1 open MV2 grounded
2nd gear MV1 grounded MV2 grounded
3rd gear MV1 grounded MV2 open
4th gear MV1 open MV2 open
TC lockup MV3 grounded.



BUT you would need MV1 and 2 to be reconnected to the TCU (and the resistors disconnected) when you have the gear selector in any of the following P , R , N...
Also remember that the TCU uses solenoid MV5 to regulate pressure to give you smooth shifts - without it being properly controlled who knows how harsh the shifts will be.
Also if you do try this REMEMBER that if you are driving at say 100 kph and decide to quickly downshift to say first gear it will do LOTS OF DAMAGE $$$$$$ so be careful..

Another thing that may interest you is that for around $20 you can build a small circuit that has 5 leds to show the state of the gearbox.
4 of the leds show you what gear the TCU has put the auto box into and the fifth led varies in brightness depending on the pressure of MV5
The 4 gear leds light up red when in that gear or green when in that gear with the TC locked.
A very handy unit that helps diagnose solenoid issues etc. Also good fun to watch !!!!

Hope this info helps.

Importantly the auto box never allows changes while the TC is locked in order to minimise wear of the clutches, hard changes and general stress of the box. Engine torque is also reduced during changes for the same reason. To operate the box manually without these criteria will drastically reduce the life of the box.
Nick