# question about making a shift box for my car

#### dmc0162

Joined Dec 13, 2007
51
I asked a similar question a few months ago about this. I have a 4 speed electronically controlled automatic transmission in my car. I want to make a box with 4 momentary buttons to select each gear. The car uses two solenoids (that require 12v) to shift the gears. The voltage from the solenoids must be applied throughout the whole gear, meaning that just a single 12 volt pulse to shift the gears will not work, the 12v needs to be applied the whole time. The gears are made using combinations of turning on two different shifting solenoids. With that said the gears go like this

1st gear: on on
2nd gearff on
3rd gearff off
4th gearn off

So those two solenoids just turn on and off to make the gears. The voltage fed to the solenoids is 12v. So what is the easiest way of making this with momentary buttons? I was told it can easily be done with relays, is this true? Also, I was told I can get everything I need to do this at radioshack. Does anybody have any ideas how I can build this? Thanks

#### mik3

Joined Feb 4, 2008
4,843
I asked a similar question a few months ago about this. I have a 4 speed electronically controlled automatic transmission in my car. I want to make a box with 4 momentary buttons to select each gear. The car uses two solenoids (that require 12v) to shift the gears. The voltage from the solenoids must be applied throughout the whole gear, meaning that just a single 12 volt pulse to shift the gears will not work, the 12v needs to be applied the whole time. The gears are made using combinations of turning on two different shifting solenoids. With that said the gears go like this

1st gear: on on
2nd gearff on
3rd gearff off
4th gearn off

So those two solenoids just turn on and off to make the gears. The voltage fed to the solenoids is 12v. So what is the easiest way of making this with momentary buttons? I was told it can easily be done with relays, is this true? Also, I was told I can get everything I need to do this at radioshack. Does anybody have any ideas how I can build this? Thanks
yes you can do it with relays and use a latch configuration to have a continuous 12 voltage on the coils

#### dmc0162

Joined Dec 13, 2007
51
Would anyone be able to draw me up a quick schematic? I am fairly new to this stuff. Thanks again!

#### rwmoekoe

Joined Mar 1, 2007
172
what is it exactly that you mean as momentary buttons?
can a 4 position rotary switch do it?
or a pair of pushbuttons, one for shifting up, the other for down?
or a pair of spst switch (you know it is a common on-off switch) that you can toggle those combinations?

#### dmc0162

Joined Dec 13, 2007
51
It CAN be done with a rotary switch or two toggle switches, or two UP and DOWN buttons, but I want to do it so that there are 4 momentary push switches. I guess there would have to be a circuit to electronically latch it if you know what I mean.

The way I want to do it is when you push momentary switch #1, it activates both solenoids, and HOLDS it on without holding the button. Then, when you want to shift gears, you push momentary button #2 which cancels button #1, and activates the solenoid necessary for 2nd gear, and so on.

#### SgtWookie

Joined Jul 17, 2007
22,210
No protection for missing a gear? IE: you wouldn't want to be buzzing along at 70 MPH in 4th, and accidentally select 1st gear, or would you?

#### Audioguru

Joined Dec 20, 2007
11,249
The automatic transmission on my car uses the brains of the computer to wait for the perfect moment to shift gears smoothly and without damage. I can hardly feel it shifting gears.
You want to shift when the timing might be the worst for the life of the automatic transmission. KA-BOOM and the tranny is gone.