Ticking over in "D"

[quasarman]

Malfunctions caused by this

I was stuck in very heavy traffic in London a while back, mostly stationary with the occasional three foot movement. I didn't even think to take the car out of D but I do now as after a while I was presented with two alarming 'Malfunction' messages on the dash, one for the ABS and the other for the traction control. After a large bowel movement and and hour parked up everything had obviously cooled down and the errors cleared themselves.

Therefore I agree with some of the previous threads, traffic lights or similar hold up D is ok, anything longer and for me its either N or P.

 

[DieselE]

The cage/gear carrier assembly rotates when in neutral, which eventually must cause some wear, though it would take a lot of idling to be a real problem unless in a "vulnerable" design I would think.

Idling in gear is as described by previous posters, but also uses more fuel than in neutral as the engine must produce enough power to not stall against the load of maintaining the oil slippage in the torque converter, hence the extra heat.

In Park, the converter is drained/relieved so the turbine/driven section will not rotate: no gearbox assembly movement, engine idling virtually freely so less fuel used.

The disadvantage on some gearboxes (more pronounced in older cars nowadays) is the slower engagement back into gear from Park.

Are you sure about the torque converter draining? AFAIK the torque converter in automobile automatic gearboxes remains full at all times. The various "gears" are selected by means of combinations of clutches and brake bands.

In neutral, both input and output blading of the TC will rotate so the pumping losses are very low. In drive, when stationary the output blading is held stationary so heat is generated. Given that the transmission has an oil cooler strain on your braking foot is likely to become an issue long before the transmission shows signs of distress.

 

[MPG]

On a related note I had my auto trans fluid, filter & gaskets changed yesterday - including draining the torque convertor this took 7 litres of fluid. The difference in quality of the shifts is amazing. Pick up of drive or reverse is now instant & gearchanges far smoother.

Also flew through the MOT without a hitch - not bad for a car just a fortnight short of it's 17th birthday !!