Gearbox questions
 

Is it true that we shouldn't put the auto gearbox in neutral all the time? a lot of people say the torque converter is not designed to act like a clutch going N and D back and forth, in traffic people should hold the brake instead of putting it in neutral?

For manual gearbox, I don't know if it will hurt the car, but I notice that as gas price goes up, people have a good excuse to shift at super ultra low engine speed, I am talking about 1200rpm and it gives you that horrible rattling sound? Any expert here?

That horrible rattling sound is detonation and will destroy an engine. Constantly shifting the auto tranny in and out of neutral when coming to stops has no benefit but can shorten the life of many internal wear items in the transmission as well as motor mounts.

if it's knocking/rattling, you're shifting too low

rattling/shaking = engine speed is too low...and in some cases you'd actually end up using MORE gas if you push the accelerator further because there is no power.

Since were kinda on this topic i have a question i've always wanted to be answered.

For example there are 2 drivers, both are accelerating to 60 km/h

Driver 1 accelerates to 60km/h with a heavy foot and harder acceleration (~4000rpm shifts) then when he gets to 60 he shifts to 5th and coasts.

Driver 2 accelerates with a very light foot and shifts at around 2-2.5k rpms, resulting in a very smooth but slow acceleration, this driver also coasts in whatever gear after they're at 60.

Which driver uses less gas in the process?

Common sense tells me shifting at 2500 is better on the internals, as well as saves gas. But there may be something to do with the lower power= push gas farther. Hmm...

^I think it would also depend on the car.

Best way to answer your own question is to do an experiment with yours lol.

Drive like Driver 1 with one tank of gas, and like Driver 2 with your next.

Put a post-it on your steering wheel to remind yourself lol

Just wondering, wouldn't driving the car to peak torque to get to the desired speed be best for fuel effciency?

for example, peak torque is at 3300rpm, I accelerate using 2nd gear to 3500ish, then shift to gear 3 to maintain it in around that area 3300rpm untill I get to the speed I want, then shift up to go to a lower crusing rpm.

peak torque/=best fuel economy

My auto shifts under 1900 rpm, but I do occasionally put it in neutral when car is still warming or in neutral in long stops