Constant up/downshifting in certain situations

[rikutoro]

Hello. I've noticed a "bug" that occurs when using a curtain type of mod. Even it's easier to experience when using a mod, I think it's still relevant for further development in ETS2, or a later game. I have analyzed the situation and eventually found out how the automatic transmission works, what triggers a downshift and an upshift. With that in mind I've figured out how this causes an undesired experience when using curtain types of mods. I've written down the event with as much relevant details as possible.

This is most notable if desired speed is set in the cruise control or if you're flooring it and have the speed limiter turned on. The bug occurs when driving in automatic mode with a constant speed and short distance between two gears. When the truck has reached the desired speed, it will depress the throttle causing the RPM to drop. If it drops below the green line, it will cause the transmission to shift down. This slows down the truck a little, flooring the throttle. It will gain speed at the lower gear until it reaches the top of the green line. Then it will shift up into the higher gear and keep accelerating until it reaches the desired speed. When this happens, the RPM drops, downshifts, and so it goes on again and again.

Here are some exceptions:

• If coming to an uphill, it will stay in the current gear.
• If going down a steep hill it may not downshift.

I've made a video where I'm driving a Scania with a 14-speed transmission in 90km/h, which is default for the speed limiter. Most of the time it will jump between 13th and 14th gear, while in hills it will stay in 14th gear. I'm having the same result when driving a Volvo. However, a 12-speed transmission is available for that brand, avoiding this problem. I haven't tested with the other brands yet, but when I'm done with this delivery I guess I'll jump back into my Volvo until the bug is fixed.

Watch on YouTube

I've pointed out some parts in the video that may be relevant.

• In the beginning of the video I have just entered the motorway and the truck is building up speed and shifting up as expected.
• At 0:40 it will shift into 14th gear, and from there the nightmare starts.
• At 1:14 I go up a hill, and it will stay in 14th gear as long as it can't reach 90km/h
• At 1:21 I enter a downhill causing it to roll faster than 90km/h
• At 1:36 it goes down to 90km/h and immediately shifts down. You'll also notice that I engage the cruise control.
• 4:35 another uphill followed by another downhill and then another uphill
• 6:55 overrev?

I'm playing the version 1.3.1s of the game. The mod installed is Realistic Physics Mod 5.0, which changes the default transmission in some trucks to 14-speed (or 12+2 if you really want to say that). Information about the mod can be found in this thread:
viewtopic.php?f=34&t=10755

I hope this will be taken a look at, and possibly fixed. Not just for the purpose of a mod, but a fix for that may be usable in the future, and maybe even improve the the shifting in the vanilla game.

[ohaha]

As you know, SCS does not provide support for modified versions of the game.
Even so, the next patch will come with a lot of tweaks and changes in RPM and engine management, so you'll have to be patient and see if this happens again.
Thanks.

[rikutoro]

Thanks for the reply!

I'll look forward to that patch when it gets released, and see if that solves the problem.

[Unco]

or if you're flooring it and have the speed limiter turned on.

Doesn't the cruise control switch off the moment you step on the accelerator? I'm not sure how the above is possible.

EDIT: Never mind the above. It was late at night and I read speed limiter as cruise control. My opinion below still stands, though.

The bug occurs when driving in automatic mode with a constant speed and short distance between two gears. When the truck has reached the desired speed, it will depress the throttle causing the RPM to drop. If it drops below the green line, it will cause the transmission to shift down. This slows down the truck a little, flooring the throttle. It will gain speed at the lower gear until it reaches the top of the green line. Then it will shift up into the higher gear and keep accelerating until it reaches the desired speed. When this happens, the RPM drops, downshifts, and so it goes on again and again.

Here are some exceptions:

• If coming to an uphill, it will stay in the current gear.
• If going down a steep hill it may not downshift.

I've made a video where I'm driving a Scania with a 14-speed transmission in 90km/h, which is default for the speed limiter. Most of the time it will jump between 13th and 14th gear, while in hills it will stay in 14th gear. I'm having the same result when driving a Volvo. However, a 12-speed transmission is available for that brand, avoiding this problem. I haven't tested with the other brands yet, but when I'm done with this delivery I guess I'll jump back into my Volvo until the bug is fixed.



I've pointed out some parts in the video that may be relevant.

• In the beginning of the video I have just entered the motorway and the truck is building up speed and shifting up as expected.
• At 0:40 it will shift into 14th gear, and from there the nightmare starts.
• At 1:14 I go up a hill, and it will stay in 14th gear as long as it can't reach 90km/h
• At 1:21 I enter a downhill causing it to roll faster than 90km/h
• At 1:36 it goes down to 90km/h and immediately shifts down. You'll also notice that I engage the cruise control.
• 4:35 another uphill followed by another downhill and then another uphill
• 6:55 overrev?

I'm playing the version 1.3.1s of the game. The mod installed is Realistic Physics Mod 5.0, which changes the default transmission in some trucks to 14-speed (or 12+2 if you really want to say that). Information about the mod can be found in this thread:
viewtopic.php?f=34&t=10755

I hope this will be taken a look at, and possibly fixed. Not just for the purpose of a mod, but a fix for that may be usable in the future, and maybe even improve the the shifting in the vanilla game.

I've looked at a good portion of your video and looked at your points above and I must say, from a mechanical background, that what you are describing is the normal and expected operation of an automatic transmission. Basically, it comes down to too low a top speed for the 14th gear to be of any use. I can only imagine that whoever designed this mod, had a removed speed limiter in mind, or a manual transmission.

Let's see what the next patch brings. The above is just my opinion and you can take it with a grain of salt.

[hippo]

I would agree that this is not a bug. If the mod is not locked, either change the limit up to 95 or 100kph, or change the gearbox ratios to allow cruising at 90kph. I use 14 and 16 speed gearboxes and they are invariably geared to hit 90 one gear short. They are intended for those that use manual gear change with no speed limiter and allow a top speed in excess of 100kph.