Bad downshift from 2nd to 1st...

[Likeanowl]

Tried searching and didn’t find anything on this specifically. When my car is downshifting from 2nd to 1st without my foot even touching the brake it will sometimes feel like I literally slammed the brake as hard as I can. Hard enough my friend has thought I hit the brakes hard to mess with him. Any idea why or what this could be a result of? No noises happen usually, sometimes a slight thud but that’s it. Maybe the diff bushing problem? Any input? Car is a 2016 DCT M3

[SD ///M4]

You shouldn't be manually downshifting from 2nd to 1st with a DCT, or a manual, as the gear differentials are too low to do this.

If you're saying that the car is downshifting to 1st automatically, it shouldn't do this as you're slowing down as the DCT will stay in 2nd until you are nearly stopped and then automatically downshift to 1st when you are stopped. If you don't come to a complete dead stop, the DCT will stay in 2nd when you start to accelerate away from the stop.

When you are in stop and go traffic and trying to pace yourself so you don't have to keep hitting the brakes, it will easily do this in 1st and even more easily in 2nd and it will not downshift from 2nd to 1st without the car being stopped.

If you are trying to downshift from 3rd to 2nd while you're slowing to a stop, you have to manually downshift from 3rd to 2nd by about 1500 RPM otherwise the car may be downshifting automatically as you are manually downshifting causing the DCT to go from 3rd to 1st.

My 2016 M4 DCT doesn't exhibit this behavior except for the 3rd -> 1st quirk as mentioned above which I learned about early on so I watch the tach as I slow down and always downshift around 1500 RPM.

[N1rve]

Originally Posted by Likeanowl

Tried searching and didn’t find anything on this specifically. When my car is downshifting from 2nd to 1st without my foot even touching the brake it will sometimes feel like I literally slammed the brake as hard as I can. Hard enough my friend has thought I hit the brakes hard to mess with him. Any idea why or what this could be a result of? No noises happen usually, sometimes a slight thud but that’s it. Maybe the diff bushing problem? Any input? Car is a 2016 DCT M3

Just DCT Things ~ but you shouldn't downshift from 2nd to first unless you're coming to a complete stop.

Mine does it pretty bad from 4th to 3rd. It's not as bad if I have the DCT in the second most aggressive shift mode (2 Bars).

[BlownOne]

If you’re going too fast or have too much rpm when you downshift it’ll be abrupt. I’ll down shift into 1st once I’m at 10-11mph and never have any issues or weird jerkiness.

[Likeanowl]

I am not doing it the car is. It shifts itself from 2 to 1 automatically right at 10mph, I watch it every time. Not sure what exactly is correct

[Narcosis]

Learn the DCT. Love the DCT.

[Beemerm3]

I always let my car shift from 2nd to 1st. If you're talking about downshifting from 3rd all the way to 1st cus u miss timed it. The jerking is there.

[Likeanowl]

No it’s 100% doing it on its own. I’m not manually shifting at all. I get that the DCT is jerky but this isn’t even a jerk... it’s like almost bringing me to a complete stop without touching anything

[SD ///M4]

Originally Posted by BlownOne

If you’re going too fast or have too much rpm when you downshift it’ll be abrupt. I’ll down shift into 1st once I’m at 10-11mph and never have any issues or weird jerkiness.

There's no reason to manually downshift from 2nd to 1st. I've never done this with a manual and I don't do this with the DCT. If you come to a complete stop in 2nd it will automatically shift to 1st.

[SD ///M4]

Originally Posted by Likeanowl

I am not doing it the car is. It shifts itself from 2 to 1 automatically right at 10mph, I watch it every time. Not sure what exactly is correct

Originally Posted by Likeanowl

No it’s 100% doing it on its own. I’m not manually shifting at all. I get that the DCT is jerky but this isn’t even a jerk... it’s like almost bringing me to a complete stop without touching anything

I said it above and I'll say it again, your DCT should not automatically shift from 2nd to 1st unless you come to a complete stop.

I can roll up to a stop sign in 2nd gear and the car will not downshift to 1st unless I'm stopped. There are some times that I thought I had come to a complete stop but I didn't and when I accelerate the car is still in 2nd gear. That would definitely be less an 10 MPH.

As I also mentioned above, I can creep in slow, stop-and-go traffic in either 1st or 2nd, depending on the speed. When I'm creeping in traffic in 2nd, mine has never automatically shifted to 1st as long as the car as rolling. Downshifting automatically while the car is rolling in 2nd gear is both unpredictable and unwanted behavior.

I've driven this car for ~35,000 in almost 4 years and it's never done this.

Edited to add: My wife drives her 2018 M3 the same way I do and this has never happened on her car either in a year and a half and 18,500 miles.

[ArialBlack]

Originally Posted by SD ///M4

I said it above and I'll say it again, your DCT should not automatically shift from 2nd to 1st unless you come to a complete stop.

I can roll up to a stop sign in 2nd gear and the car will not downshift to 1st unless I'm stopped. There are some times that I thought I had come to a complete stop but I didn't and when I accelerate the car is still in 2nd gear. That would definitely be less an 10 MPH.

As I also mentioned above, I can creep in slow, stop-and-go traffic in either 1st or 2nd, depending on the speed. When I'm creeping in traffic in 2nd, mine has never automatically shifted to 1st as long as the car as rolling. Downshifting automatically while the car is rolling in 2nd gear is both unpredictable and unwanted behavior.

I've driven this car for ~35,000 in almost 4 years and it's never done this.

Edited to add: My wife drives her 2018 M3 the same way I do and this has never happened on her car either in a year and a half and 18,500 miles.

My car shifts to 1st when you slow down to about 5kmh (or 3mph) after closely monitoring it. This only happens when your foot is on the brake.

I too was a victim (or should I say culprit) of accidentally shifting the car at too low of RPM in 3rd and both car and I shift at the same time straight to 1st. The sound is ungodly...

[BlownOne]

Originally Posted by SD ///M4

There's no reason to manually downshift from 2nd to 1st. I've never done this with a manual and I don't do this with the DCT. If you come to a complete stop in 2nd it will automatically shift to 1st.

There’s plenty of reasons...going up a steep hill, wanting to hear my exhaust blip, needing to accelerate quickly, wanting to hear my badass exhaust setup haha.

I actually used to think the same thing about downshifting into 1st until I figured out the sweet spot (10-11mph) to do it at and it’s just seamless.

Op, are you saying the car automatically downshifts from 2nd to 1st when you’re in manual mode or auto? I noticed in auto mode with my transmission shift setting on two the downshifts are fairly abrupt and jerky.

[Likeanowl]

Originally Posted by BlownOne

Op, are you saying the car automatically downshifts from 2nd to 1st when you’re in manual mode or auto? I noticed in auto mode with my transmission shift setting on two the downshifts are fairly abrupt and jerky.

It’s doing it in auto mode. Just tried it again. Was going about 35 mph, saw a stop sign so I applied the brake until I hit about 20mph then let off the brake and just let the car decelerate on its own. When the car hit exactly 10mph it was in 2nd and AUTOMATICALLY downshifted to 1st with a huge jerk almost as if I hit the brake. The whole time it was in auto mode. I did not touch a shift paddle or gear shifter at all. To clarify, I was in auto mode. Once again, I was in auto mode. But just to be clear... I WAS IN AUTO MODE. NO MANUAL SHIFTING INTERVENTION FROM ME AS A HUMAN BEING OCCURRED.

I don’t get why people keep saying “well stop down shifting until you stop”. I’m not the one doing it, the car is doing it on its own without me touching anything. I guess I’ll say it again.... The. Car. Is. Downshifting. On. It’s. Own. Without. Me. Touching. Anything. From. 2nd. To. 1st. At. 10mph.

[White340]

Was it in auto mode? 😂. Jk..

I sometimes downshift from 2nd to 1st at 8-9 mph just to hear the exhaust when coming to a stop. Is this really that bad?

FWIW OP, my car doesn't downshift hard when doing this at least for now with 8k miles on it.

[ntg44]

Have there been any DCT software updates since 2016? May be worth a shot.

[SD ///M4]

Originally Posted by Likeanowl

It’s doing it in auto mode.

This is the first post where you've mentioned that you're driving in Auto mode, not sequential. You did say "I’m not manually shifting at all" but that was referring to your car downshifting on it's own, and that's not the same as saying that you were in Auto mode. All of my replies were based on the assumption that you were driving in Sequential mode and you waited too long to manually downshift from 3rd to 2nd. Perhaps you should have mentioned this in your first post. I feel like I've wasted too much time on this post now.

Regardless, something is not right.

[RaviG292]

This is a weird one. Have you tried to see what would happen in S mode? Shift down to second while coming to a stop and then wait see if it automatically goes to first early causing the jerk or if it goes down smoothly after you are nearly stopped?

Side Note: I also shift down to first at the sweet spot between 9-11 mph before coming to a stop to hear the exhaust blip like some others have mentioned😁.

[MR RIZK]

Easy way to rule out the car just go and test drive a demo and see if it does the same. If it does great, if not least you can demonstrate yours is different if still under warranty.

[Likeanowl]

Little update, noticed it only happens in sport+. In efficient it stays in 2nd until I stop.

[TrueNorthM5]

To me it sounds like a issue with your transmission software. If stock and on warranty just mention it to the dealer. If no more warranty you could try a transmission tune.