rough downshifting

[vstolpner]

Originally Posted by NormB

x281 here. With no evident pattern this car very rarely makes a VERY harsh downshift from 2nd to 1st--always when moving at a crawl. It is sometimes quite disconcerting.

Never have seen this between any other gears.

That's probably when the car thinks you're engine breaking. Try going into "manual" and downshifting a couple gears to cause it to engine break and you should notice the same jerkiness as you mention.

[black-box]

I have the 6-speed. It lunges forward a bit when it drops from 2 to 1 while slowing to a stop in my parking garage. Which is disconcerting when there's a parked car right in front of me.

[improvius]

Originally Posted by vstolpner

That's probably when the car thinks you're engine breaking. Try going into "manual" and downshifting a couple gears to cause it to engine break and you should notice the same jerkiness as you mention.

I think vstolpner is exactly right: it's the adaptive transmission doing a poor job of interpreting my driving style.

Background:

I'm driving a 2015 X28i with paddle shifters. And I use the paddles frequently. (They're the single best optional feature on the car, IMO.) I'm also willing to bet that most of the folks here having rough downshifts likewise have and use the paddles.

Most of the time when I use them, it's to downshift early when slowing. I do this either for engine braking or for pushing through a turn in a lower gear. They work great for my purposes, and I use them like this all the time in daily driving.

Sometimes, though, I just want to drive smoothly (like when I have passengers), so I'll forgo the paddles and just let the auto box do its own downshifting. The problem is that it isn't all that smooth. Each time it blips down a gear, the whole car jerks back noticeably. It's nothing dangerous, but it's super annoying.

What I think is going on:

The adaptive transmission has "learned" to downshift earlier than it needs to. Because whenever I override it, that's exactly what I do. Granted, it's not downshifting nearly as early as me, but I think it's doing its best to approximate my shifting style. This is a problem because I constantly want to switch back and forth between two different "styles:" smooth downshifting and aggressive downshifting.

My workaround:

What caused the problem also provides the solution. I now use the paddles to put the transmission into manual mode whenever slowing. But if I want to slow smoothly, I just leave it in a higher gear. This forces the car to stay in the current (high) gear until it has to downshift to avoid bogging. Which is exactly the opposite of my aggressive, high-gear slowing. And the result is a perfectly smooth downshift.

The obvious "downside" is that I need to manually intervene all the time if I want smooth downshifting. But since I already enjoy using the shifters, this isn't really a big inconvenience to me. It's just frustrating that this supposedly advanced technological feature ultimately ends working against the driver.

[Alfisti]

It's my biggest issue with the car, tranny is rough as guts. The whole drive train is fucking brutal, no class at all, super disappointing, my 2008 9-3 shits all over it for refinement of the drivetrain.

[vstolpner]

Another option when slowing just put the car into neutral - no shifting of any kind in that case.