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bulkwarrior 08-13-2012 12:37 PM

a silly question about the transmission
 
I was told by someone long time ago that if you put the transmission in neutral during a traffic stop, it will save the transmission and prolong its life. Can someone tell me if this is true or not? I usually do this and it seems the car vibrates a little less(I have a 2006 X5 4.4i E53). My car isn't vibrate a lot but I can feel it when I stop at a traffic light in "drive". If I put it in neutral I can't feel it no more.

Thanks.

TerminatorX5 08-13-2012 01:29 PM

i think this is an urban myth stemming from use of manual xmission by people who never drove stick... in manual you have to in neutral but automatic is not designed this way...

Anyone can chime in?

bulkwarrior 08-13-2012 01:46 PM

I've driven stick, and I usually keep the stick in first gear when I'm at traffic stop. Just keep the clutch half engaged, and when light changes depress gas pedal and fully engage the clutch.

SlickGT1 08-13-2012 02:00 PM

Well two wrong thing bulk.

1. Putting an automatic trans into neutral effectively cuts off line pressure. When you put it in drive, you up the pressure. This actually causes more stress to your trans.

2. Keeping an manual in gear, and holding the clutch, is effectively feathering the clutch that whole time. If you know how the parts look, and function, you will understand that a pushed in clutch pedal, does not always detach fully. You still have slight surface to surface contact. Going into neutral is better. When you engage the clutch, all you are really doing is spinning the oil in the trans. This is actually good for it. As all components are still getting lubed, even though you are standing. This also does not wear any clutch parts.

TerminatorX5 08-13-2012 02:03 PM

:iagree:

TwinTurboGTR 08-13-2012 02:07 PM

Term is right. Modern Auto trannys do not need to be shifted in Neutral to prolong its life. It actually becomes more harsh on the tranny because the clutch pads are constantly in use; from going out of gear and then back in gear. Some say it shortens the life and some the opposite. In my opinion, if you look at a transmission, it wasn;t built to be constantly taken out and put back in gear.

So I am assuming when you hit a light, your hitting the brakes and shifting into neutral. Then when you stop, the light turns green and you shift back into drive. Now that may be fine, but what about if you still rolling to a stop and and in neutral. Do you shift it back into drive and then go??? I'm sure you aren't coming to a full stop if it was in that situation. So the clutch pads are put in a situation where they weren't designed to be used.

its the same argument with a manual. When people come to a stop, they will double clutch and downshift and use engine breaking to slowdown and use the brakes at the very end. When some choose to shift into neutral and use all brakes. SO what's the difference? Some argue that the first way, you wear the clutch out faster because you are doubling up on gear use and for the second method, people say you will wear out brakes faster. IMHO, brakes are a whole hell of a a lot cheaper and easier to replace than a clutch.

As for vibration, I don't notice mine does but I've noticed my other cars to that sometimes. Its mainly because the tranny is in first and is engaged, so you hitting the brake is causing a counterforce for the tranny wanting to go. When you place it in neutral, there is not force.

Koody 08-13-2012 02:11 PM

I dont know if putting the autobox in neutral will prolong its life, what i do know is that it will help prolongen the life of your rotors because you dont have to use the brakes like you do when the autobox is in Drive when waiting for trafficlights , so the brakes can cool off evenly instead of getting bent by the difference of temperature on the rotors and where the brakepads are.

When i drove stick, i put it in neutral and depressed the clutch entirely when waiting somewhere for some reason. This will have less wear on certain parts of the clutch/trans system.
Anyone other ideas?

My 2c

@TwinTurboGTR: +1

TerminatorX5 08-13-2012 02:15 PM

As far as the engine vibration, there might be a different problem altogether, internal to the engine, and transmission only emphasizes that problem.

You might want to check to see if all of your cylinders are firing properly, if none of them is tarded and the other things... I would not know how to approach this problem but I would think, it is a problem. How is your emissions? You pass it ok? MAF?

I think INPA can read some of the values off a running engine, I just don't know what those values should be - I am sure there are more experienced people here and elsewhere who could chip in...

bulkwarrior 08-13-2012 02:31 PM

OK. I don't know much about modern tranny design but think this way, when you are at a stop, your engine is revving at 700RPM and your wheel is not moving. That discrepancy must be handled by the tranny. some parts in the tranny are translating that axle coming from engine that's moving at 700RPM, and the drive axle going to the wheel that's not moving(because the wheel's held by the brakes). Shouldn't there be a clutch or something in the tranny that's grinding this whole time?

SlickGT1 08-13-2012 02:33 PM

Quote:

Originally Posted by bulkwarrior (Post 891177)
OK. I don't know much about modern tranny design but think this way, when you are at a stop, your engine is revving at 700RPM and your wheel is not moving. That discrepancy must be handled by the tranny. some parts in the tranny are translating that axle coming from engine that's moving at 700RPM, and the drive axle going to the wheel that's not moving(because the wheel's held by the brakes). Shouldn't there be a clutch or something in the tranny that's grinding this whole time?

It is called the torque converter, and it slips on purpose for this reason. lol.


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