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Old 08-14-2013, 12:19 PM   #201
GregOrz
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I have been reading about downshifting and decelerating. If you are just driving normal and placid and you want to gradually decelerate over a long distance from 60 miles per hour from top gear... is it better to downshift your way to 2nd until you come to a stop OR can you just throw it into neutral, let off the clutch and just gently brake till you stop? Like will neutral deceleration preserve transmission components?

I know its dangerous to aggressively brake from high speed while your in neutral, I'm talking about extremely mild braking with gradual deceleration.
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Old 08-14-2013, 12:46 PM   #202
cheezmunky
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Originally Posted by GregOrz View Post
I have been reading about downshifting and decelerating. If you are just driving normal and placid and you want to gradually decelerate over a long distance from 60 miles per hour from top gear... is it better to downshift your way to 2nd until you come to a stop OR can you just throw it into neutral, let off the clutch and just gently brake till you stop? Like will neutral deceleration preserve transmission components?

I know its dangerous to aggressively brake from high speed while your in neutral, I'm talking about extremely mild braking with gradual deceleration.
Some people will argue that it is better to downshift for safety reasons because your car remains in gear, and you are able to give it throttle in an emergency situation.
Another argument for downshifting is that it uses less fuel. Engine braking should use little to no fuel as the momentum keeps the pistons moving whereas in neutral gas is required to keep the engine idling.

On the other hand, downshifting causes more wear on your clutch and synchros.
It could also be considered unsafe if not using your brakes at all because inattentive drivers may rear-end you.

I think overall it is just driver choice. I personally leave my car in whatever gear it's in or downshift a single gear and use the engine braking as a complement to my brakes. The only time I use engine braking as the main source of braking is in poor road conditions, such as snow, where the brakes may or may not help. Once again, this is just my take and I'm sure that others' vary.
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Old 05-28-2014, 08:01 PM   #203
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^i slip into neutral when slowing down, especially from highway speeds I have also noticed that by doing so it's less wear on the trans and my mpg has gone up on average 1mpg it's win win in my book, of course do it according to the given conditions.
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Old 05-28-2014, 09:06 PM   #204
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^i slip into neutral when slowing down, especially from highway speeds I have also noticed that by doing so it's less wear on the trans and my mpg has gone up on average 1mpg it's win win in my book, of course do it according to the given conditions.
Makes absolutely no sense.

Your MPG wont go up by slowing in neutral because instead of a full fuel cut by engine braking, you end up burning fuel.

You also burn up the brakes a lot faster because theres nothing holding you back. The entire drivetrain is freewheeling instead of having rolling resistance.

It also wont be less wear on the trans. How can you even determine its less wear on the trans without tearing the trans apart or having data from a UOA or otherwise?

Your whole post is talking out your ass
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Old 05-29-2014, 10:25 AM   #205
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^ all I can say is try it. I get average22-23mpg mixed city and highway. Works for me!
10+ years as a mechanic it's just theory! I'm not here to internet battle!
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Old 05-29-2014, 10:50 AM   #206
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^ all I can say is try it. I get average22-23mpg mixed city and highway. Works for me!
10+ years as a mechanic it's just theory! I'm not here to internet battle!
Your theory doesnt hold any water...

Especially in a constant mesh transmission where if the wheels are moving and the clutch is engaged the internals of the trans are still moving.

And the MPG is in your head, a placebo if you will. If you were engine braking the injectors would be off where while you are coasting in neutral the injectors are firing to keep the engine running.

Factual data wins over thoery any day of the week.

I would still like to know how you can say its less wear of the transmission without any proof whatsoever.

Last edited by 2Fast4U1DAY; 05-29-2014 at 04:29 PM.
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Old 05-29-2014, 11:20 PM   #207
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Let me ask you this. Ever used a truck for hauling heavy loads? Increased loads increase wear in all areas. I understand everything is freewheeling sort of speak, but there is less load resulting in less friction=less wear on moving parts. Yes they still move but the force behind them is at a min. And this also translates into your mpg.

What you are telling me is I'm doing 70mph and am approaching a 4 way stop that it is better to use engine braking threw each gear at varying rpm along with braking to a stop? Vs placing the car in neutral slightly in advance to applying brakes letting engine rpm drop to a constant 8-900 rpm until the car is at a stop? Do this over a period of 1 tank full and my mpg will be better than yours every time and while braking with the trans in neutral their isn't a positive or negative load on the trans resulting in less clutch and gear wear.
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Old 05-30-2014, 12:54 AM   #208
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Originally Posted by Luke17 View Post
Let me ask you this. Ever used a truck for hauling heavy loads? Increased loads increase wear in all areas. I understand everything is freewheeling sort of speak, but there is less load resulting in less friction=less wear on moving parts. Yes they still move but the force behind them is at a min. And this also translates into your mpg.

What you are telling me is I'm doing 70mph and am approaching a 4 way stop that it is better to use engine braking threw each gear at varying rpm along with braking to a stop? Vs placing the car in neutral slightly in advance to applying brakes letting engine rpm drop to a constant 8-900 rpm until the car is at a stop? Do this over a period of 1 tank full and my mpg will be better than yours every time and while braking with the trans in neutral their isn't a positive or negative load on the trans resulting in less clutch and gear wear.
I didnt say anything about downshifting

Yes I have my CDL and drove OTR for 2 years.

If you increase the gross weight, yes you will increase the load, however the load does not change from the standpoint of decel in gear versus coasting in neutral because no matter what you arent changing the vehicles gross weight just by throwing into neutral. You are still moving the same amount of weight therefore you are placing the same load on the transmission.
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Old 05-30-2014, 08:25 AM   #209
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Not to add to either side, here is my experience:
I get a solid 26mpg consistently (2L Turbo 2005), and my driving by preference usually involves one downshift per decel from 60 to a stop, usually to third. If I'm decelling from 60 to 20ish for a spirited corner/intersection where I'm planning on carrying speed or accel out of, I double into 2nd from 5th.

I had my trans torn apart by TiC at 120k, Tony reports all my syncros are in newish condition. My original clutch was still at 30%.

Take that however you feel. My advise is: shift how you like, as long as you are not damaging anything. Your preference is more important than MPG.
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Old 12-07-2015, 08:11 PM   #210
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thanks for all the info
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Old 12-14-2015, 01:13 PM   #211
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Awesome! Thanks for sharing!
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Old 10-14-2016, 07:01 PM   #212
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I'm just here to thank the great Unabomber for this awesome thread!
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Old 10-15-2016, 09:23 PM   #213
jw4902
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Great info here. I usually speed match the car speed to engine rpm when down shifting, instead of double clutching, but its worked for 45 years- haven't had to replace a clutch yet. If I should be double clutching instead please let me know. Thanks.
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Old 10-18-2016, 02:32 PM   #214
AaronCompNetSys
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Originally Posted by jw4902 View Post
Great info here. I usually speed match the car speed to engine rpm when down shifting, instead of double clutching, but its worked for 45 years- haven't had to replace a clutch yet. If I should be double clutching instead please let me know. Thanks.
Double clutching isn't to save your clutch, it actually wears it more. It is to save your syncros on the gears. Syncros are designed to generate friction and have some wear in their lifetime, but won't last forever without care. Going down one gear at a time is fine without double clutching, but in most cases you should double when skipping more than one gear. The exception is 2nd -> 1st gear, Subaru recommends in most owner's guides to never shift into first while rolling due to very high chance of wear. My opinion is that while difficult (and high chance for a mistake), double clutching into first can be safely achieved with little syncro wear, all they way up to the redline. I try not to do it often since I still haven't mastered it.

Its not required but doubling can be useful going up gears. For example when I redline it in second gear and then plan to shift to sixth, I'll double and rev match as needed.

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Old 09-13-2017, 12:31 AM   #215
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Default Clutchless shifting

Nothing on the art on shifting without the clutch tho. And I mean up and down shifting. Sure up shifts are easy if u know what your doing, just like on a sport bike. Down shifting is a lil harder but with rev matching it's very easy with the right touch and experience. Allows for left foot braking and less fancy foot work. in a hurried brake into a corner where u need more concentration on steering and watching mirrors a heel toe mistake can ruin you your entry, Apex, and exit. But not for faint of heart or inexperienced since a gear grind is no good, but if done right no grind and very quick shifts.
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