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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.

TerminatorX5 08-13-2012 02:36 PM

:iagree:

bulkwarrior 08-13-2012 02:39 PM

ok, if the torque converter is slipping, wouldn't that shorten it's life? If the torque converter is shot the tranny is bad, right?

TerminatorX5 08-13-2012 02:46 PM

by the same token using the brakes will shorten the life of the rotor... the TC has longer lifespan than the rotor but just because you use up the rotor's life, you will not stop stopping... that sounds weird - stop stopping... hmmm... i need to go home - too much time at work... lol...

SlickGT1 08-13-2012 02:50 PM

Yes there are clutch packs in the torque converter. They are oil pressure controlled. See again, we are back at oil pressure. Taking away that pressure, and applying it at every stop is not good. You don't give the trans enough time to re-establish that said pressure, and then take off. Brakes are much cheaper, use them.

If the TC blows up, yes, it could grenade into the transmission, taking transmission with it. You will feel shuddering and whining when the TC is failing.

bulkwarrior 08-13-2012 03:02 PM

On average, how long(how many miles) does a X5 auto tranny last? My X5 is 110k miles. Had another small car whose tranny needed replacement at 170K. I had to donate it because the cost of replacing tranny exceeded the remaining value of that car. Does anyone here had to replace their X5 tranny? At how many miles? Thanks.

blktoptrvl 08-13-2012 03:19 PM

Quote:

Originally Posted by TwinTurboGTR (Post 891167)
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.

Also...

When you come to a stop in a manual, you should put it in neutral and let go of the clutch pedal, otherwise you are putting unnecessary pressure on the hydrolics (or cable if is is old style). Even worse, you are putting a lot of wear on the throw-out bearing.

You have to go through all the same pain to replace this bearing as you do the entire clutch when it wears out so you might as well replace all clutch components at this time. All unnecessary expense.

JCL 08-13-2012 03:59 PM

No benefit to putting an automatic transmission in neutral or park at a traffic light. It is also less safe, since it eliminates the opportunity to move in the event of a pending collision. There is a miniscule amount of heat created by the torque converter at idle, easily handled by the cooler. Bulk, don't think of the torque converter as a clutch. It is a fluid drive, as opposed to a mechanical drive. When there is insufficient pressure (ie at idle) the drive is not engaged. Nothing is wearing. Your are turning one part of the torque converter, and that creates a slight drag, which lowers your rpm just enough (in your case) to feel a vibration. Adjust the idle and that will go away. The clutch packs in the torque converter that were mentioned above are not part of the drive at idle, they are lock-up clutches only used at higher road speeds, nothing to do with sitting at idle.

With a manual transmission, you should be in neutral at a traffic light. Sitting with your foot on the clutch will get you a fail in a driver's license exam, because it is considered that if your foot slips off the clutch you will shoot out into traffic. More importantly, when you have your foot on the clutch for an extended period of time you are abusing the throw-out bearing. Blktoptvl, I read the whole thread before someone (you) mentioned the throwout bearing, I couldn't believe it. Seems manual transmissions are a dying breed, lol.

bulkwarrior 08-13-2012 04:03 PM

Thanks, JCL, your post is very knowledgeable and insightful. When I drove a stick(long time ago), the primary reason for me to put the foot on the clutch and engage it a little is, there are a lot of slopes in this area. When I stop at a upward slope, I had to do this because otherwise the car will slip backwards and scare the people behind me. LOL.

JCL 08-13-2012 04:10 PM

That is even worse, because you are wearing the clutch as well as the throw-out bearing.

Both our daughters learned to drive a stick at 16. We lived on the side of a mountain. They had to do repeated start/stops on hills, at every four way stop, and in several different vehicles that all had different clutches. I taught them with the use of the handbrake, but the driving instructors wanted them to be able to do it without touching the handbrake. It is all in the coordination.

SlickGT1 08-13-2012 04:18 PM

Quote:

Originally Posted by JCL (Post 891197)
No benefit to putting an automatic transmission in neutral or park at a traffic light. It is also less safe, since it eliminates the opportunity to move in the event of a pending collision. There is a miniscule amount of heat created by the torque converter at idle, easily handled by the cooler. Bulk, don't think of the torque converter as a clutch. It is a fluid drive, as opposed to a mechanical drive. When there is insufficient pressure (ie at idle) the drive is not engaged. Nothing is wearing. Your are turning one part of the torque converter, and that creates a slight drag, which lowers your rpm just enough (in your case) to feel a vibration. Adjust the idle and that will go away. The clutch packs in the torque converter that were mentioned above are not part of the drive at idle, they are lock-up clutches only used at higher road speeds, nothing to do with sitting at idle.

With a manual transmission, you should be in neutral at a traffic light. Sitting with your foot on the clutch will get you a fail in a driver's license exam, because it is considered that if your foot slips off the clutch you will shoot out into traffic. More importantly, when you have your foot on the clutch for an extended period of time you are abusing the throw-out bearing. Blktoptvl, I read the whole thread before someone (you) mentioned the throwout bearing, I couldn't believe it. Seems manual transmissions are a dying breed, lol.

No one mentions the throw out bearing, because those that know how to drive, don't destroy them. Most of us don't even change the clutch till 150k miles. And quite a few of us, can still shift without a clutch. lol. Yes manuals are a dying breed, which is a shame. I am looking for a 3.0 X5 on stick though. So hopefully I will get my first manual SAV. Keeping the 4.8 though.


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