Automatic Transmission Shifting Logic...

[NJC2]

There are a few issues I have noticed with the transmission shifting logic that I think should be addressed. I never noticed it until they added own-able trailers, and I posted about this a few years ago and it still persists in the game (even ETS2). When pulling an empty trailer, the transmission tries to start in a higher gear than when without a trailer. It's most noticeable on high HP/torque engines. For example, with a 600HP engine and an Eaton 18-speed, with no trailer the transmission starts in 5th gear. This is fine, however when I hook up to an empty trailer it will try to start in 6th or 7th gear. It's like someone accidentally programmed the starting gear wrong using a +gear instead of -gear when hooked to an empty trailer. When coasting to a stop, the transmission downshifts to 1st or 2nd gear, and while sitting still, it shows it's in A1 or A2, but as soon as you touch the accelerator it immediately shifts up to the higher gear. With a 600HP engine, it can handle it, but it's slow to accelerate, and it's quite annoying while parking.

When I was messing with different transmissions while testing this, I noticed it does not happen with the Allison TC10, but it has its own annoyances. No matter if empty or heavily loaded, It always starts in 1st and revs to 1900 RPM before shifting to 2nd and revving to 1900 and then it skips to 4th gear. That's especially annoying when driving slowly in town or parking and your engine is revved up to 1800+ RPM. I can toggle it to manual and when empty or lightly loaded, it can easily start in 2nd and shift at 1500-1700 skipping gears, or when heavily loaded it can start in 1st and still skip gears shifting at 1500-1700. There is no need to rev so high and use 1st and 2nd gears on a level surface.

[AvidSurvivalist]

To add to this, I have an issue with the W900 with Eaton Ultrashift 18 spd not downshifting when using the engine brake. I have to keep hitting the downshift hint key multiple times to get RPMs up enough for effective engine braking, then it has the nerve to shift back up!

[The_SimTrucker]

The engine parameters (note NOT the transmission parameters) have some settings that influence the shift behavior. See https://modding.scssoft.com/wiki/Docume ... ngine_data

Defaults are:
rpm_range_low_gear (700, 1500)
rpm_range_high_gear (1000, 1350)
rpm_range_power (1400, 1900)

My guess is that the "rpm_range_power" is causing the high rpm before shifting that you do not expect on a flat surface and/or with light loads. You can try to set that to a lower range to try to force the rpm's down and force the transmission to upshift earlier.

As for the Allison TC10: that is a real automatic with a torque convertor and not an automated manual. Modeling the stall speed of the torque converter is something that can be improved.