@11qazxc thanks! I will test it out and tell you the results!

Pitch*clamp01((Time-smooth(Time,abs(rate(GS<V1))?9999:0))>T1)*clamp01((Time-smooth(Time,abs(rate(GS<V2))?9999:0))>T2) .... *clamp01((Time-smooth(Time,abs(rate(GS<Vi))?9999:0))>Ti)
V1,V2...Vi is speed at which 1,2...ith gear switches in meters per second.
T1,T2...Ti is time 1,2...ith gear needs to switch.

@SteamPunkPilot I'll test it later

@ReinMcDeer changed those &amp and &Lt correctly, still doesn't move.

@SteamPunkPilot i think you put an extra * because of the italics
Try
Pitch*clamp01((GS>50 & GS<50+1))*clamp01((GS>80 & GS<80+2)

&amp are more than symbols and &lt are less than

@ReinMcDeer update: it's working, but when I add another gear it just doesn't move.

Edit: this is the code I put in the Inputcontroller section of the engine

Pitchclamp01((GS>50 & GS<50+1))*clamp01((GS>80 & GS<80+2)

I put it in input.

@SteamPunkPilot
As requested
https://www.simpleplanes.com/a/y8Q0T3/PA-PX-532ST-WORKING-AUTO-TRANSMISSION

@SteamPunkPilot Yep

@Griffon1 I would like to see it!

@ReinMcDeer where should I add this to?

I'm guessing the engine?

I know... I'm slow...

I've actually coded an automatic transmission.
I borrowed some code from a manual transmission and modified it to shift at certain rpms.
It's rough, but it works.
The manual transmission also had editable gear ratios in the variables so that was kinda cool
I havent uploaded it yet, but I'd be willing to if you'd like to take a look.

I've thought about this too
Probably something like:
Throttle*clamp01((GS>a & GS<a+x))
Throttle can be changed to whatever you're using for the engine
a = Gear change speed
x = The smaller this is, the shorter the gear change
Add more *clamp01((GS>a & GS<a+x)) to add more gears
I don't know if car engines have throttleResponse as a variable, but if it does, set it to 1