Weird lurking noise when going slow

[rfernatt]

Sounds like the usual drivetrain/gearbox rattle/clacking noise at low speed when no gas is applied and the car is creeping sort of jerkily forward while the engine is idling. If you can keep your foot on the gas just a hair, it will smooth out and not make this noise at a constant low speed. But, even then, in drivethrus or other start/stop situations at low speed you'll still hear it briefly.

[SmartDigger]

Could be the clutch engaging the pressure plate.

[bikerboy]

Pardon my spelling...yes lurching is what I meant. Anyhow, so I guess its normal but everything should be fine because I have a warranty so I'll probably take it down to the mechanic one of these days before the warranty expires. I actually hear a noise when I turn the wheel to the left and to the right when the car is standing still. Is that normal too? The best way I could describe it is a "farting" type of noise.

[Godfather]

I definitely want to be the fly on the wall when the service writer tries to address "my car lurches and farts."

[PeteInLongBeach]

The low speed rattling from the transmission is transfer gear lash noise due to the transmission configuration and vibrations from the 3-cylinder engine. My 3-cylinder Honda Insight also did this. They all do this, and it is completely normal.

[Terry Stibal]

I wonder about the "shift points" set for the automatic mode of the transmission. The same thing holds true for the "arrow" upshift indicator on the dashboard display.

I find when "relying upon the machine" to make the shifting decisions that the transmission often ends up with the engine "lugging" along at too few revolutions for the speed selected. My gut feeling is that the engine is best suited to driving the car when above 2,500 RPM, and offers the best part of its torque from 3,000 RPM up to about 5,000 RPM.

I imagine that the low RPM shifts are primarily designed to boost fuel economy, and they do appear to do that, based upon our limited experience with our car to date. If it were in my power to change the way the transmission works, I'd up the shift points a bit.

The way that the transmission functions in the Smart vehicle reminds me of the early automatic ("Hydromatic") transmissions in some light US armored vehicles at the end of World War II (and early 1950's civilian automatic transmissions such as the 1955 Chevrolet) shifted. With all of those, there was that same "moment of uncertainty as the transmission decided that it was time to move to a higher gear - not at all like we have come to expect with "modern" automatic transmissions over the past fifty years.

[rfernatt]

Originally Posted by Terry Stibal

If it were in my power to change the way the transmission works, I'd up the shift points a bit.

It is - just use manual mode!

[Terry Stibal]

If I do (or, more importantly, if my wife (who is not into shifting for herself (pardon the pun)), then the transmission is no longer "automatic" then, is it?

The low shift points seem to be more of an irritant when operating at low highway speeds. Fifth gear can enter lugging territory whenever more than a minor hill is encountered, as others have noted, but the transmission wants to stay in that high gear in the worst way.

With everything under the Smart sun apparently under computer control, it would seem that this issue too would be "configureable". It's not a deal killer, but it is a minor irritant.

One thing about the Smart that is pretty neat is that you can use the manual shifting option either from the steering wheel paddles or from the floor mounted shift lever. (Our Scion xB only offers this from the floor mount.) However, the location of the floor lever isn't very convenient if you have an arm rest installed and in use.

[jwight]

For the leventy-seventh time, the smart will/does not "lug." If/when the computer senses the rpm are not sufficient, it will downshift or add power as needed.