It's not sound related, it's just that the car surges forward when coming to a stop. I'm not adding gas either, only brakes.

what do the revs do when you downshift? just the normal blip or anything extra? do you have a bluetooth obd to log rpm and speed while testing this a few times?

I don't have a bluetooth OBD unfortunately, but let me try to describe the best I can so you can replicate this (maybe?).

You're at 35 MPH, 2nd gear at around 3000-4000 RPM, approaching a red light that's 5 car lengths away. Cute girl on the right side of the sidewalk, shift into 1st gear, car blips, revs up to around 5000 RPM and you brake while coming to the light, the girl gives you the 'wtf, what an asshole look". Now as you're at around 10 MPH with your foot on the brake, as you think the car will come to a complete stop, the car surges forward again, like a jolt.

You are trying to downshift going way too fast. Max speed in first is like 35-38mph (don't recall exactly) and the car will NOT let you downshift into max speed anyway as that is already redline. It is probably saving you from an overrev by not engaging right away but instead blipping and hanging the rpms until you slow down before engaging into gear

Basically don't downshift into first going so damn fast and you shouldn't have a problem.

I'll tell you exactly what it is. When you shift into first at that speed, you engage the lockup converter, and the surge you feel at 10 mph is when the TCU has to take pressure off the lockup converter in order to unlock it. Shifting into first at that speed is hard on the trans, and I wouldn't recommend it. 10 mph is when the speed of the car starts to slow down the engine below a preset point, so the TCU commands the lockup converter to disengage.

What he said^^^^^

Like everyone else, if I manually shift from 2nd into 1st at around 10 MPH while coming to a complete stop, the car surges a little bit. When I let the trans shift itself, I don't feel it nearly as much. This is exactly why I seldom manually shift into 1st gear.

IMHO, the only circumstance I could see it being necessary to shift from 2nd into 1st is if you're cruising at like 15-20 MPH in 2nd gear, and want to accelerate quickly, in which case, the car handles it perfectly and doesn't surge at all.

-J.B.

I bet it's just the engine coming back to life. Under engine braking fuel is completely cut. At around 1200-ish RPM (I don't remember exactly) injectors start ticking again and the engine surges a little.

MTs do it too.

I have a gm truck with a heavily modified 4l60e with a lot higher than stock shift pressures. It does the same thing. It's a non issue. Every auto does it on the 2-1 shift. It's just more pronounced because the computer ups shift pressures in automanual mode.

Patient: "Doctor, it hurts when I do this."

Doctor: "Don't do that."

I engine brake all the time with my AT, but not from 2nd to 1st.

Hi All,

It's fine for your AT to downshift into 1st from 2nd IF (a big IF) your BRZ/FRS has a working "rev matching" feature.

If you downshift into 1st and the car feels like it's slowing down due to engine NOT blipping the throttle for you, it may be something like I experienced.

I even made a video about it to show the dealer. Note, the car will NOT let you downshift into 1st if you are going too fast in which your speed with exceed redline in the speed you are going.

In my situation, rev matching would stop after driving 30+ mins in "D" mode. To fix it temporary, I had to restart the engine.

I took my BRZ to the dealer yeasterday and showed them the video I made. They flashed new updated software to the TCM (Transmission Control Module) and so for so good it's fine.

Anyways here's the video. Is the engine "surge" you guys experiencing what I experienced as rev matching not working when downshifting? Hope this helps.

[ame="https://www.youtube.com/watch?v=AYN19T7ySVo"]BRZ Rev matching failure (Automatic 6 Speed 2015) - YouTube[/ame]

Skip to 1:00 where I start downshifting.

Vic

So my car started doing this also around 10mph whenever I'm slowing down. I'm just driving in its normal mode. Automatic. Right when I hit 10-11mph it surges and slows down abruptly

Just because you can....doesn't mean you should.....

How many people downshift to 1st on MT when rolling to a stop? And I bet you it's just as rough feeling