[Evan]

2017 Smart Transmission Thud when starting from a stop. I have a 2017 Smart passion 900cc with 20K km. When the road has a slight incline downwards and I'm letting my foot off the break pedal (with D engaged) I feel a thud with a metallic sound (Click) coming from the engine compartment (transmission), and then the car starts to push forward. The same happens if I have R engaged, and the road has a backward incline. When the road is straight, or even a bit uphill, this never happens. Anyone else experiencing this? any ideas?
Thanks so much!

 

[Apexerman]

Hmm, I can't say I've heard or felt that in my 2016 Proxy. It's not unusual to hear rattling from the back when slowing to a stop or just beginning to accelerate, but that's relatively normal for the twinamic DCT (Dual Clutch Transmission). Do you keep the drive mode in the (E) Economy or switch to (S) Standard? I personally find the Standard setting creates less noise than Economy and the car simply behaves better with a little more revs at hand. As for a thud, it sounds like a hard shift. It's possible the clutch packs may be trying to find the right moment of engagement. Are you hitting the throttle when this thud occurs or just letting off the brake? Perhaps the lack of resistance of a flat or inclined surface complicates the shift action. Couple that with the very non-linear drive-by-wire throttle and it might be a hard shift as the engine revs build. Speculation of course. Perhaps others may have direct experience. I know I've learned to carefully modulate the throttle on takeoff due to the momentary delay in power.

 

[Evan]

Hmm, I can't say I've heard or felt that in my 2016 Proxy. It's not unusual to hear rattling from the back when slowing to a stop or just beginning to accelerate, but that's relatively normal for the twinamic DCT (Dual Clutch Transmission). Do you keep the drive mode in the (E) Economy or switch to (S) Standard? I personally find the Standard setting creates less noise than Economy and the car simply behaves better with a little more revs at hand. As for a thud, it sounds like a hard shift. It's possible the clutch packs may be trying to find the right moment of engagement. Are you hitting the throttle when this thud occurs or just letting off the brake? Perhaps the lack of resistance of a flat or inclined surface complicates the shift action. Couple that with the very non-linear drive-by-wire throttle and it might be a hard shift as the engine revs build. Speculation of course. Perhaps others may have direct experience. I know I've learned to carefully modulate the throttle on takeoff due to the momentary delay in power.

Thanks so much for your response. I also have a 2016 Passion that does all the rattles you are mentioning when approaching a stop. The 2017 does not do that, just the clicking when letting the break pedal at a slightly sloped road. I use the E drive mode (I thought the S stands for Sport, haha). Rattling from the back is heard from both cars, and others I see on the road. I feel like the clutch is disengaged thinking I'm going down a garage ramp or something, an then putting the 2st gear in?
The thud comes .5 second after I let go of the break without touching the gas pedal. I let the car start to roll before I put my foot on the gas. I generally take it easy and like to drive passively. The S mode certainly makes the car operate more sporty.

 

[Falcon WIng]

What about the "hill start assist?" Could the brake be sticking a bit just before releasing? I'm thinking this since you mentioned it happens on inclines...

 

[Bob Ricewasser]

What about the "hill start assist?" Could the brake be sticking a bit just before releasing? I'm thinking this since you mentioned it happens on inclines...

I believe that hill start assist lightly engages the clutch, not the brake.

 

[Falcon WIng]

I believe that hill start assist lightly engages the clutch, not the brake.

Reading the owners manual, it says the term "Brake your vehicle..." I took that to mean brakes....not clutch. However, it doesn't say definitively. I would like to know the answer to this.

 

[Evan]

What about the "hill start assist?" Could the brake be sticking a bit just before releasing? I'm thinking this since you mentioned it happens on inclines...

The clicking is heard and felt when starting from a stop with the shifter in D, only when there is a small slope downwards. If the slope is backwards as the car is at a stop and the shifter is on the R position, the same clicking/thud happens as it does when in D position with a slope downwards.
If there is no slope, or a slope upwards, everything works and sounds normal.Does that help?

 

[Silver Bullet Smart]

Check your motor mounts! Mine did same, replaced all 3 and it went away.

 

[Evan]

Check your motor mounts! Mine did same, replaced all 3 and it went away.

Thank you so much! That was my initial thought, but the dealer dismissed it without even checking the mounts. I will certainly schedule a visit and have them check. I will circle back with an update

 

[OliverB]

Check your motor mounts! Mine did same, replaced all 3 and it went away.

This was an issue for the 451 smarts but hasn’t been, so far, for the 453. Did you replace them on a 451 or a 453?

 

[Evan]

This was an issue for the 451 smarts but hasn’t been, so far, for the 453. Did you replace them on a 451 or a 453?

Have you noticed any heavy clicking when in D mode and letting your foot off the break pedal (only when the road has a downward slope)?
When the road is level or uphill this does not happen with my 453.

 

[OliverB]

Have you noticed any heavy clicking when in D mode and letting your foot off the break pedal (only when the road has a downward slope)?
When the road is level or uphill this does not happen with my 453.

No, haven’t noticed heavy clicking. Only issue I had was rough downshift into 2nd and 1st, especially in hot weather and with the AC compressor engaged. Transmission software upgrade cured most of that issue.

 

[Silver Bullet Smart]

This was an issue for the 451 smarts but hasn’t been, so far, for the 453. Did you replace them on a 451 or a 453?

it was in my 451, good to know

 

[Evan]

No, haven’t noticed heavy clicking. Only issue I had was rough downshift into 2nd and 1st, especially in hot weather and with the AC compressor engaged. Transmission software upgrade cured most of that issue.

My 2016 453 does exactly the same, when the air is engage it gets worse . My 2017 does not have this issue at all

 

[OliverB]

My 2016 453 does exactly the same, when the air is engage it gets worse . My 2017 does not have this issue at all

Have you had the software update done? The 2017 most likely came with it.

 

[Evan]

Have you had the software update done? The 2017 most likely came with it.

No I have not done an update on my 2016, MB asked for $250 for the 10K mile oil change so I only had them change the oil and filter. next time I will have them do it

 

[OliverB]

No I have not done an update on my 2016, MB asked for $250 for the 10K mile oil change so I only had them change the oil and filter. next time I will have them do it

I complained about the shifting while still under warranty and the dealer applied the update w/o charge.

 

[Evan]

This was an issue for the 451 smarts but hasn’t been, so far, for the 453. Did you replace them on a 451 or a 453?

The Smart service vendor told me this is definitely not an engine mount issue and suggested they check the software at my next visit