Changing Gear While On Drive

[udana_k]

Hi all,

i was advised by one of my friends to change the gear position from D to N while on drive. the idea is to save more fuel. i doubt if this a good practice.. do u guys do like that on your auto gear cars?

Thanks

Udana

[varunatech]

Shifting from D to N or D to 2 (or vice versa) will not do any harm to the transmission. BUT, letting a car roll on neutral can be very tricky as there is no engine breaking available. Specially if you are going downhill. When going downhill without the engine break you will melt the breaks and finally loosing it all. In some countries there are laws against coasting (driving in neutral).

Finally better not on flat land. Never in downhill.

(By the way in some transmissions, if you shift from D to 2 at a very high speed where the 2nd gear cannot operate, the electronics will not downshift until you come to a tolerable speed for the 2nd gear)

[The Don]

  On 1/11/2012 at 10:58 AM, udana_k said:

Hi all,

i was advised by one of my friends to change the gear position from D to N while on drive. the idea is to save more fuel. i doubt if this a good practice.. do u guys do like that on your auto gear cars?

Thanks

Udana

Personally I think this is a bad idea and not good practice to begin with.

A. You should not be running a car on neutral on roads because you are not in control of the car anymore, as in you can't accelerate on demand in reaction to a road situation and you will not have the extra assistance you get to slow down the car.

B. Every time you shift gears it causes wear and tear on your auto box or for that matter any gear box. Why do you want to wear down your gearbox with unnecessary gear changes?

[NRX]

and on top of all you won't be saving fuel by cruising downhill on neutral, you burn more

I don't know whether this applies to all cars but usually when you take the foot off the gas when you are going downhill the injectors cut off the fuel supply to the engine, a thing I got to know recently

[varunatech]

  On 1/12/2012 at 4:10 AM, NRX said:

and on top of all you won't be saving fuel by cruising downhill on neutral, you burn more

I don't know whether this applies to all cars but usually when you take the foot off the gas when you are going downhill the injectors cut off the fuel supply to the engine, a thing I got to know recently

What you say is available in some new models of Euro and US cars to save gas. They are fitted with different engines and starter motors to start the engine quickly. Other normal ones cannot cut off fuel as the that will stall the engine

[miniace]

Varunatech I really dont know who taught you tech stuff or where you found the stuff you mentioned, The fact remains shifting up or down of an auto tranny in speeds above 20km/h is VERY BAD for the box.

As NRX elaborated, just take the foot off...game over for the fuel burning issues.

Advising members here is good, misleading is extremely bad. If you are so sure post it, else save other peoples cyber space, time, money and lives.

MINIACE

[Kavvz]

  On 1/11/2012 at 10:58 AM, udana_k said:

Hi all,

i was advised by one of my friends to change the gear position from D to N while on drive. the idea is to save more fuel. i doubt if this a good practice.. do u guys do like that on your auto gear cars?

Thanks

Udana

I would advise against that.

1. Shifting the car into neutral (N) while driving / cursing along (either on a flat or down hill) with the gear selector in neutral (N) will cause the automatic transmission to spin and heat up but as the car isn't in drive (D) there won't be an adequate supply of transmission oil to cool it, thereby over heating it and ruining it / shortening its lifespan.

2. Shifting from drive (D) to neutral (N) or vice versa, when the transmission is spinning at high rev's causes strain on the transmission as well, which again in turn shortens the lifespan of your transmission.

[varunatech]

MINIACE,

I have no intention of misleading any member. Please note that in a automatic transmission, shifting between 2nd, 3rd and 4th while driving is safe and that is how it is designed.

Please note my explanation here applied to Hydraulic Automatic transmission and do explain use 4 speed gear boxes.

The OD ON/OFF button will make sure you cannot shift beyond the 3rd gear and you can apply it when running on 4th gear. The system will shift you down to three. Also if you put OD to on, while you rev faster (reaching the limits of 3rd gear) the system will automatically shift you to 4th gear.

Apart from OD button you can move to 2nd and D position depending on the driving condition (the amount of engine break you need or torque you need).

The above driving is practiced and also stated in owners manual.

Only thing is you cannot or should not shift to first or R gear. That is why you have an interlock tied with the button and the foot break. You should never do that.

The Auto transmission shifts is initiated by electrically driven actuators and those are actuated by a set of electrical pulses. Though we have a lever in the car, we actually depress a set of switches. And the system is designed to shift between these gears and also the system can put it to first gear in case of a higher torque requirement.

You definitely would have have seen steering mounted gear switches in sports models. They are meant to switch across gears. Those switches also actuates.

The system also actuate the valves, we also do the same by shifting the lever.

It is correct and doable to shift between 2, 3 and 4. And also for CVT gear steps. Mind you not for the 1st and R.

Please correct me if I have done any mistake, and do reiterate has no intention of misleading anyone.

Thanks..............

[slcamel]

  On 1/12/2012 at 5:40 AM, miniace said:

As NRX elaborated, just take the foot off...game over for the fuel burning issues.

MINIACE

+1

[Gyiman]

My understanding & from what others/ I have read is that shifting between gears & trying to mimic a manumatic in a standard auto is bad. I have also heard stories of people busting their GB from excessive engine braking.

Don't see the point in people trying to do this sorta thing in order to 'save' fuel, your better off getting a push bike or taking the bus.

[terrabytetango]

I had shifted to 2 instead of D after backing up out of the parking lot, and shifted to D at around 60ish when I noticed the shift into 3rd didn't happen. All that happened was that the car found the next gear, no drama. However shifting into neutral is risky, not only due to what is stated above, but due to a pothole or carelessness, you might shift into reverse instead, and that's when the proverbial excrement will hit the fan. This had happened to a newish Nissan Caravan, my mechanic told me.

Edited January 12, 2012 by terrabytetango

[varunatech]

  On 1/12/2012 at 8:43 AM, Gyiman said:

My understanding & from what others/ I have read is that shifting between gears & trying to mimic a manumatic in a standard auto is bad. I have also heard stories of people busting their GB from excessive engine braking.

Don't see the point in people trying to do this sorta thing in order to 'save' fuel, your better off getting a push bike or taking the bus.

One clarification.........about what I have posted

I am not talking about mimicking Manumatic or fuel savings...........both are crappy ideas.

But shifting to 2nd, and 3rd through OD OFF are standard ways of handling the vehicle when engine breaking required, when sudden torque is required, or some times engaging "SNOW" button when available to take less torque when coming out of slippery grounds.

Hope this clarifies............

Edited January 12, 2012 by varunatech

[Gyiman]

Why is a manumatic a crappy idea?

[varunatech]

My Apologies, mimicking the manumatic is what I meant. Manumatic is not crappy........

Did change the post with correct wordings.....and thank you.

Edited January 12, 2012 by varunatech

[varunatech]

  On 1/12/2012 at 9:52 AM, Gyiman said:

Why is a manumatic a crappy idea?

My Apologies, mimicking the manumatic is what I meant. Manumatic is not crappy........

Did change the post with correct wordings.....and thank you.

Edited January 12, 2012 by varunatech

[Sylvi]

  Quote

Hi all,

i was advised by one of my friends to change the gear position from D to N while on drive. the idea is to save more fuel. i doubt if this a good practice.. do u guys do like that on your auto gear cars?

Thanks

Udana

Udana,

If you want to save fuel have a free wheeling system fitted to your system.

Under mentioned one way clutch bearings I got from the web .

you will have to fabricate same to the drive shaft.

have to have a method to lock when you do not want the freewheeling

you can change gears without the clutch when you are on free wheel.

One way clutch (Freewheels) : The application of clutch is for economic solution, to reduce the cost compared with separately controlled couplings/brakes, ratchet arrangements etc; in some design. Clutch is preferred to conventional solutions because of its advantages in operating safety & better automatization. No Driving Contact between inner & outer ring, while in rotation, in one direction and driving contact between inner & outer ring, which transmit torque in the other direction of rotation.These Clutches should never be dismantled at users end.

To minimize critical stresses in keyway area of inner ring keyways have radius instead sharp corner, hence the Keys must be chamfered on their edges. Read more

Sizes other than Specified are on request

Data

Torque:110 to 3200Nm

Sprag type, with bearing support. Tapped holes on face to mount part.

Bore size:- 14mm to 180mm. Torque:200 to 80000Nm

Sprag type, with bearing support,

enclosed condition.

Bore size: 12mm to 75 mm

Torque: 335 to 5760Nm

Sprag type, with bearing support.

Bore size:14 to80 mm

Torque: 360 to 8200Nm

Roller ramp type, with bearing support,

enclosed condition.

Bore size: 14mm to 80 mm

Torque: 165 to 6580Nm

Roller ramp type, with bearing support,

enclosed condition.

Bore size: 14mm to 120mm

Torque: 90 to 14400Nm.

Torque: 220 to 4700Nm

Sprag type, without bearing support.

Sprag type, without bearing support.

Centering of outer ring is required.

Model ND-Bore size:12mm to 45 mm

Model NMF - shaft required hardened & ground.

Torque: 130 to 1530Nm. Model NDF - Bore size:34.92 to 69.85 mm

Model NDF shaft required hardened & ground.

Torque: 190 to 690Nm

NMD

Technical Data

The Functions of clutches

Indexing / Feeding : is to convert motion either from a continuously rotating shaft on intermittent basis OR by converting the reciprocating linear motion of a Pneumatic / Hydraulic cylinder into an intermittent rotary motiion.The rotary motion of the drive shaft is converted into an intermittent rotary motion by means of a hold pin and connecting rod attached to arm of the freewheel whose arc of index can be varied as required by adjusting slot. Especially when clutch is used as a indexing clutch, the Key connections must be free from play. The best indexing application is reached with unalloyed oils with a low degree of viscosity.

Overrunning: The inner ring can rotate faster then the outer ring in same direction of input and if stopped inner ring continues to rotate of input and if stopped inner ring continues to rotate at input speed and vice versa. E.g. if a large motor or turbine has to be up to speed, by a slow speed starter motor, the use of freewheel between these elements enables the starter motor to be shut down without any mechanical involvement. If a freewheel is interposed in a drive between a gearbox / a large machine, the freewheel prevents any back drive OR damage to gearbox if at all any power failure. In this function, if the direction force / rotation changes, there will be automatic obstruction of connection between the component(s) and coupled machine.

Backstopping / Holdback: The Purpose of backstopping is to providing a return OR reverse lock. This smoothly permits rotation of the drive shaft by overrunning in one direction but immediately locks if the shaft by attempts to go on reverse, such as in inclined conveyors, elevators etc. in case of power failure OR motor is switched off, to avoid the conveyor load from running back.

Lubrication: Most clutches especially indexing and clutches with high speed overrunning are provided with unalloyed, acid free, low viscosity oil. Oil must be changed initially after about 80 operating hours & there after approximately 1500 operating hours .depending on the environment, refilling up to 1/3 level.

Sylvi Wijesinghe

[Sylvi]

Members,

there were few DKW Cars had the free wheeling system came to Ceylon in early 1960s.

I do not know there are any of them existing at present.

Sylvi Wijesinghe.

[miniace]

Varunatech, no offence machan but too much of googling the wrongly and inconsiderately written articles mislead most.

Honestly didnt read your last clarification, but if you still unyielding the statement that shifting auto tranny when moving is fine, surely you may stick to it. I will repair it FOC when you mess your one by doing that on condition that you correct your statement (for the benefit of all innocent AL users, surely I will skip my roster and stay in SL and take a weekend off to do it my self and explain).

If you can visit my poor stable I can show you few trophies of busted auto trannies.

For the benefit of the others...DONT SELECT GEARS WHEN MOVING !

THE END

[varunatech]

  On 1/13/2012 at 5:24 AM, miniace said:

Varunatech, no offence machan but too much of googling the wrongly and inconsiderately written articles mislead most.

Honestly didnt read your last clarification, but if you still unyielding the statement that shifting auto tranny when moving is fine, surely you may stick to it. I will repair it FOC when you mess your one by doing that on condition that you correct your statement (for the benefit of all innocent AL users, surely I will skip my roster and stay in SL and take a weekend off to do it my self and explain).

If you can visit my poor stable I can show you few trophies of busted auto trannies.

For the benefit of the others...DONT SELECT GEARS WHEN MOVING !

THE END

Thank you and appreciated your input, and please read my previous explanation if time permits, following are further explanations.

My comments here are not based on just articles, but on technical details of a Automatic transmission. Also the owners manual of cars advice to shift from 4 to 3 (OD OFF) and also to 2nd gear for further engine breaking.

The soft switch OD ON/OFF is meant to shift gears while moving at high speeds (high RPMs). Why they are there, if that is harmful and put by the manufacturer themselves.

In some systems the gear shifting does not occur if the RPM is too high for the given gear ratio and wait until it slows down. One such example is once one of my friends while cruising at 160kmph, he shifted to 2nd gear to get more power to overtake another car (In a foreign expressway). But his system did not downshift until he slowed to 120kmph, where the RPM was in safe region for 2nd gear.

By the way All AL members, please read your car manuals and follow the instructions for gear shifting.

And I do humbly state (for the benefit of all members who has read and will read my posts), I have no formal education on Automobile engineering. All I do posses is 1+ year helper job experience in a garage. Advice and guidance from a very experienced Auto engineer. My own research and DIYs, information from some manufacturers and local engineers. Basic electrical, electronics, thermodynamics and mechanical engineering knowledge and passion for any engineering subject. The intention of myself is not to put anyone in difficult situations or mislead, but to share the knowledge and help.

[miniace]

  On 1/13/2012 at 12:49 PM, varunatech said:

The soft switch OD ON/OFF is meant to shift gears while moving at high speeds (high RPMs). Why they are there, if that is harmful and put by the manufacturer themselves.

Dude...OD on off is not for that... read more please....OD engagement delays if RPM is high since the power ratio is exceeded the output .(Ratio=1/ (1+S/R)= 1 (1+36/72) = 0.67:1) This is a simple typical example.

  On 1/13/2012 at 12:49 PM, varunatech said:

My comments here are not based on just articles, but on technical details of a Automatic transmission. Also the owners manual of cars advice to shift from 4 to 3 (OD OFF) and also to 2nd gear for further engine breaking.

Regulating gears is fine thats why the choices are given ,provided you do them on low speeds but never toggle from D to R or vice versa.

Anyways suggest you read a bit more...just a simple and a very friendly advice..love it or leave it.

MINIACE

[varunatech]

  On 1/13/2012 at 4:50 PM, miniace said:

Dude...OD on off is not for that... read more please....OD engagement delays if RPM is high since the power ratio is exceeded the output .(Ratio=1/ (1+S/R)= 1 (1+36/72) = 0.67:1) This is a simple typical example.

Regulating gears is fine thats why the choices are given ,provided you do them on low speeds but never toggle from D to R or vice versa.

Anyways suggest you read a bit more...just a simple and a very friendly advice..love it or leave it.

MINIACE

No problems in your advice...........

But I sense that you have misunderstood few of my quotes, probably I have not mentioned it right here...........

Cheers............

[varunatech]

  On 1/13/2012 at 5:19 PM, varunatech said:

No problems in your advice...........

But I sense that you have misunderstood few of my quotes, probably I have not mentioned it right here...........

Cheers............

By the way, I would stop commenting further as two of our discussion may mislead other forum members. As a general comment, would ask the non tech savvy members to stick to their manufacturers advice.

[varunatech]

By the way, I would stop commenting further as two of our discussion may mislead other forum members. As a general comment, would ask the non tech savvy members to stick to their manufacturers advice.

[Dhanushkapg]

Moving Gear Lever to D to N is bad if it happen all the timesx. some times ago i also doing such crazy thing. when car is on traffic i suddenly turn gear lever in to N . One day my gear stopped shift Bcus the cable between gear lever and gear box comes out of the pin from gear lever side.Dont do it anymore

[Nilantha]

  On 5/22/2012 at 12:15 PM, T-Bag said:

If you want to change the gears in middle of the road, why do you need a Auto Box? Use a manual one.

If you don't know what you are talking about, please keep quiet ok? thanks.

[Black Death]

  On 1/12/2012 at 4:10 AM, NRX said:

and on top of all you won't be saving fuel by cruising downhill on neutral, you burn more

I don't know whether this applies to all cars but usually when you take the foot off the gas when you are going downhill the injectors cut off the fuel supply to the engine, a thing I got to know recently

Dude come on man! how can you b burning more fuel when your cruising in neutral? unless you dont take your foot off the gas pedal that is! lol

if the fuel is cut off from the injectors, then the engine will stall. the only time 'fuel cut' kicks in is when the engine over revs above the limit and the ECU cuts the signal to the fuel pump to minimise or prevent engine damage. Hope you got this sorted out.

Edited May 22, 2012 by Black Death