This model is base on the Allison 1000 automatic transmission. Is not an exact replica but the basic design and functionality are the same. The most significant difference from the real transmission is the C1 and C2 clutches that I design to work with 3D printed parts and for easy engagement.

Gear ratios:
1st: 3.20
2nd: 1.86
3rd: 1.43
4th: 1
5th: 0.70
6th: 0.60
R: 4.41

I made the lower part of the case quite big so there's room to put solenoids to engage all the clutches and even a parking pawl to control them with switches or even change gears automatically with something like Arduino.

The selector 3D model is here: http://www.thingiverse.com/thing:1214373

If you want the Arduino sketch to control the solenoids, send me a personal message. I currently have the sketch working with lights instead of solenoids because I don't have the transmission printed yet. Is very realistic with all the features you could expect: Select Park, Reverse, etc, with delay on Reverse and Drive mode, has automatic mode changing gears considering speed and how much pedal is press (require a speed sensor on the output and a potentiometer for the pedal), has manual mode, manual override, etc.

I don't have a 3D printer so I would appreciate any feedback from people that printed one to improve the model. Still, I check all parts on Cura to make sure all is ready to print, except the orientation. You will have to rotate some parts to print it in the optimum way to have the least overhanging and warp.

Last update: 06/05/2016