Auto's and Idling

[Abb0]

Hey there team,

A quick question for a Friday morning, what is everyone's opinion in regard to shifting out of gear (D) when at the lights/in a traffic jam? I would've thought that it would save a little fuel, not much I know but maybe a little.

I've heard, although I don't particularly believe it, that idling an auto' (in neutral) is bad for the gearbox (sorry, transmission  ). Anybody that actually knows if this is the case?

Thanks
   Paul

[Chris Longhurst]

Paul
I actually tried this last summer to see if it made any difference. In the grand scheme of things, it made zero net difference to the amount of fuel the engine used over the course of each tankful. Idling in 'D' shouldn't do any damage to the transmission because the torque converter is designed to allow exactly that

[Abb0]

Hey Chris,

I was more thinking does it damage (long term) the transmission if left in N while idling. I have been told it does but that was some time ago and Auto technology has come a loonnngggg way since then 

Cheers
Paul

[Weerwolf]

I have a car with a viscous coupling LSD. This works in a similar way to a torque convertor on an auto trasmission. I was told that when the oil inside the VC gets hotter , it becomes thinner , and provides more locking.

Could the same thing happen in a torque convertor ? If your driving the car hard , the oil gets hot and the convertor locks more. Could this than damadge the transmittion , if left in gear when idling ?

[Chris Longhurst]

I doubt it. Think about it - when accelerating, braking or driving normally, the gears in the transmission are under incredible stress because of the resistance of the car to move vs. the power coming from the engine. When you're standing still and the engine is idling, the stress on the internal components is miniscule compared to what it is when you pull away. And the torque converter itself is designed to have one side stationary while the other side spins.