Re: Automatics : P or N at signals / traffic lights? Quote:
Originally Posted by funkydevil Putting the car on D at signals only keeps the car in gear and will wear your brake pads faster. | Quote:
Originally Posted by androdev Realistically, transmission wear is not so bad that you would incur expenses due to stopping in D mode. I would be more concerned about brake lights and brake pads which have much shorter life if care is not taken. -) |
Brake pads don’t really wear when the car is stationary. Quote:
Originally Posted by androdev P mode is same as N mode with transmission locked with a mechanical 'pin'. Should not be used without locking the wheels with brake because this 'pin' can wear and break. Trying to hold the car at stop with P mode is equivalent to stopping the car with a 'pin' that locks the transmission shaft. Can put a lot of stress on this pin if the car is on incline ,etc. so P mode should always used with brakes just like N mode. I would like to think that P mode doesn't exist for the driver and it is just meant for the car's computer to use P when you switch off, AT breakdown, etc.
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So here is a picture of this mechanical pin, known as pal. It fits very snuggly into a meshed gearing wheel.
I attended a workshop just last week at a Jaguar specialist who also specialises in overhauling autotransmissions. Obviously, Jaguar but he gets work from Mercedes, BMW, Audi, Porsche dealers and a few others as well. Also, he is a forensic investigator for various car insurances.
He actually discussed the case where a BMW owner made a claim on his insurance. His car had been rear ended by a truck and dragged across the road for about 15 meters. Obviously, there was a lot of damage. In addition the owner claimed the auto transmission was damaged as well. So the insurance called Raymond and send him the transmission.
He told us it would be extremely rare for a transmission to get damaged by a rear end, no matter how severe. This particular box had all sorts of problems, none related to the car being in parked whilst rear ended.
Here some more information on this story and transmission in general: http://www.team-bhp.com/forum/diy-do...ml#post4180547
We actually did ask Raymond about what damages could/do happen when you leave an autobox in D and keep the car on the brake. According to him, again, you need to get real unlucky before anything happens. Ambient temperature (say well above 40oC) and a box that has never had a refresh is a combination that could give problems. But not within seconds, or minutes. You would have to hold it for 15-20 minutes at least, or repeatedly for many intervals. Under those circumstances you could actually boil the transmission fluid. Transmission fluids, like lubrication oils are full of dopes. These dopes do deteriorate over time. They all do and that is one of the main reason there is simply no such thing as an autobox sealed for life (Even though Jaguar will still sell you one!). All boxes at some point in time need a flush to get rid of all debris and dirt and a re-fill.
The older the transmission fluid the more likely it is to give problems, especially at higher temperatures. Simple draining and re-filling is just about the worse you can do to an autobox. (See the example in my thread). On the upside, it would be very rare to damage anything even if the transmission is running very very hot. Even the brain and all other parts should have no problems with those high temperatures. So as soon as you manage to get a flush and a refill everything is likely to work as before again.
Even so, I do believe you should never put your car in P until you are actually parked, i.e. not participating in traffic anymore. My Jaguar still has the gorgeous J-gate. I can switch between D and N and vice versus with a little flick of my wrist. Don’t need the brake or push any buttons. Works great!
Jeroen
Last edited by Aditya : 20th April 2017 at 09:48.
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