[zenx]

Originally Posted by amk_2009

To be honest, I dont really notice my gear changes while driving. May be I am too much used to my Scorpio. I do not look at RPM before shifting gears. Everything depends upon driving conditions and driving actions happen as they should. Only when I notice something and want to pay more attention, I give attention to additional input. I am much comfortable with feedback from my Scorpio in terms of slight engine sound / vibration to decide my driving style.

But I never felt the need to skip any gear in my cars during last 10 years of driving.

May be mine is too old driving style.

Pretty much the same. I do it on "feel" - when I've revved enough on 3rd and don't expect to accelerate/push the engine much after the upshift, I guess this happens. Also, happens much more on the OHC than on dad's Indigo - the latter mostly on a mild downhill when there's barely any push on the pedal needed anymore.

[honeybee]

Originally Posted by swiftdiesel

There is the 4th gear for a reason and I do not upshift from 3rd to 5th. There will be considerable lug in the engine and transmission with any dose of rev matching. Personally, I don't do it and won't recommend it.

Downshifts though are a different story. When I'm braking from a 100 to a crawling 20, I cannot downshift sequentially (unless I have the time) and I reckon it is perfectly alright to do so. In fact, one cannot do a 4th in 20 km/h. So yeah, upshifts, strictly sequential, downshifts, as the situation demands.

There are two schools of thought here.

One says that as long as you are within the applicable rpm or speed range for a gear, you can shift into that gear, from any lower or higher gear. This means if my car can cruise in the fourth gear at speeds above 40kmph, as soon as I cross 40kmph, it's safe to shift into the fourth and let the car cruise. Whether I was in second gear or fifth doesn't matter.

The other says that the sequence of shifting must be observed and that if the third gear is available, it should be used instead of shifting directly from second to fourth.

However from the second school of thought I perceive a feeling that it's ok to downshift and skip a gear, but it's NOT ok to skip a gear while upshifting. I want to know exactly what is it that makes it ok to skip a gear while downshifting but not ok while upshifting.

[Guna]

Originally Posted by honeybee

However from the second school of thought I perceive a feeling that it's ok to downshift and skip a gear, but it's NOT ok to skip a gear while upshifting. I want to know exactly what is it that makes it ok to skip a gear while downshifting but not ok while upshifting.

One difference is that, when you downshift from 4th to 2nd, you would have brought down the engine speed as well by directly braking (without operating clutch). At this point both engine RPM and vehicle speed warrant 2nd gear.

[honeybee]

Originally Posted by Guna

One difference is that, when you downshift from 4th to 2nd, you would have brought down the engine speed as well by directly braking (without operating clutch). At this point both engine RPM and vehicle speed warrant 2nd gear.

That's already taken care, since I have qualified the argument by saying the speed of the vehicle and the RPM match the gear I want to shift into. So if I wanted to shift down from fourth to second, I would ensure the RPM and the speed are within the range of the second gear.

Plus it's not really a difference as nowhere I find anyone advising to upshift or downshift (skipping gears or not) at a stage where the existing RPM/speed does not match with the intended gear selection.

So my original question still remains: Why is it ok to skip gears while downshifting but not while upshifting?

[supremeBaleno]

From purely a perception/feedback POV, it seems safer IMO to skip while upshifting than downshifting. Assume someone tries to upshift from 2 to 5 when the rpm is not high enough - at best the engine will lug and we will correct. But assume someone downshifts from 4th to 1st at high rpm without first using brakes - the feedback provided by the car/engine in this case won't be as subtle as in the former.

@ACM, I have done that changing gears (up and down) without using the clutch on my CD100, just for the heck of it after reading somewhere that you don't really need a clutch to change gears. But I don't have the balls to try it on my car.

[IndigoXLGrandDi]

@supremebaleno..
You would have read about changing gears without clutch on shell website.
I too had read it on that website.
But now the page has been removed from the website.

@all..
Also, while downshifting as long as the resulting RPM is within the "handling" range of the engine, I don't think it would have ill-effects on the engine. As far as ill-effect on gearbox is concerned, it will be on the synchroniser rings only.
Experts please correct me.

[skandyhere]

Originally Posted by dheepak10

Shifting from any gear to neutral is fine and would not have any impact on the engine/gear components.

dheepak10,

I was asking about shifting FROM neutral TO the 5th directly, assuming that the vehicle speed is appropriate for the 5th.

Originally Posted by honeybee

So my original question still remains: Why is it ok to skip gears while downshifting but not while upshifting?

I think that's a very important question. My interpretation of some of the previous posts leads me to believe that the point is, the wider the difference in RPM for each gear shift, the more wear on the synchroniser. This is a guess; not knowledge.

In any case, I am finding it very difficult to believe that there is little wear from the violent increase in RPM during an 'aggressive' downshift whereas there is greater wear from having to pull the RPMs down further during what feels like a smooth upshift when one skips a gear.

This is interesting, and I'd like to understand it in greater detail.

[chetanhanda]

Originally Posted by dheepak10

Well, here's my two cents on this topic from what I gathered from various sources:

Most modern manual-transmission vehicles are fitted with a synchronized gear box. In a synchromesh gearbox, to correctly match the speed of the gear to that of the shaft as the gear is engaged the collar initially applies a force to a cone-shaped brass clutch attached to the gear, which brings the speeds to match prior to the collar locking into place. The collar is prevented from bridging the locking rings when the speeds are mismatched by synchro rings. The synchro ring rotates slightly due to the frictional torque from the cone clutch. In this position, the dog clutch is prevented from engaging. The brass clutch ring gradually causes parts to spin at the same speed. When they do spin the same speed, there is no more torque from the cone clutch and the dog clutch is allowed to fall in to engagement. In a modern gearbox, the action of all of these components is so smooth and fast it is hardly noticed.

When you shift from 3rd to 5th, the synchronizers get a little more wear since they have to pull the RPMs down further with the longer gear ratio shifts you're doing, because the RPM for a speed of 40kmph @ 3rd gear is more than the RPM for 40kmph @ 4th gear, which in turn is more than 40kmph at 5th gear. Say you shifted from 3rd at 5000 RPM, to 5th. The synchronizer would have to pull the clutch disk RPMs down from 5000 to about 2500 or 3000. A normal shift from 3rd to 4th only has to drop the RPMs a few hundred or so.

But then, the damage is not immediate, but happens in the long run.

In the case of downshifting, we generally tend to skip gears only when the speed reduces significantly. So, it should have the same ill-effect as in the case of upshifting.

(1) I really dont think syncros are so weak that there will be damage in the long run..syncros can take a lot of beating.I have been driving manual boxes quite "hard"for quite some time now and dealt with older cars with high mileages - never had any syncro issues.(drove auto for just a year only)
(2) Shifting from 3rd to 5th is no big deal that too with a stock vehicle ..there will be a slight drop in rpm with the stock(heavier) flywheel - not so much to actually make the syncros work harder.
(3)Your theory of "clutch disk rpms coming down to 2500 from 5000" :
Can you explain this a bit more clearly ? I'm not quite getting the point.

[ambivalent_98]

What about downshifting from 5 to 3 ?
Lets say you are 5th and you have to slow down suddenly but not come to a dead halt say from 80 kph to about 25-30 kph , do you still go through 5 , 4 , 3 or have you done 5 to 3 directly ? I have done this a couple of times. I ain't no auto expert but will this affect the engine ?

[honeybee]

I have been shifting down from fifth to third very regularly, right since my M800 days, which is to say about six to seven years, and I haven't had any premature clutch or gearbox failure anytime. So I can safely say this practice doesn't cause any abnormal wear and tear of the gearbox components.

I have also sometimes indulged in the practice of coasting in neutral and then shifting into fifth the moment the speed slackened a little bit (this was majorly with a Uno diesel), so again as long as you keep the speeds within limits of the fifth gear, shifting from neutral to fifth shouldn't be a problem (you may experience a slight jerk as the gear engages).

[supremeBaleno]

^^^Could you please elaborate on the scenario where you would "coast in neutral and then shift to 5th" ?

BTW, a google search for "is skipping gears bad" puts out a host of links - apparently this is being discussed on a lot of forums.

[honeybee]

Well, when I was not much literate about cars, engine braking and such (those were days before TBHP was born ), like the other drivers I saw, if I hit a long slope, I would shift into neutral (engine still running) and let the car coast, using an occasional tap on the brakes if the car started picking up too much speed. After the slope was over and the car was on level road, or maybe an ascent, I would shift into fifth (the car would be doing close to 60kmph then), release the clutch gently and then accelerate.

[prakash_ajp]

Well, I am sure many people skip gears while downshifting. And I do that too, often. But up-shifting, only occasionally. When I am in third gear and want to overtake someone in a hurry (imagine two slow moving trucks in adjacent lanes), I have to push the engine to 3000+ RPM and when I am done passing, the speed would be more appropriate for the 5th gear than the 4th as per my regular driving patterns. I think it's totally okay and can't do any harm to your car.

[skandyhere]

Originally Posted by supremeBaleno

BTW, a google search for "is skipping gears bad" puts out a host of links - apparently this is being discussed on a lot of forums.

supremeBaleno,

Would be useful to see some material/views you find on other forums (in case you're pursuing this subject further) shared here in case you find something seemingly trust-worthy.

[supremeBaleno]

I did look up some of the links thrown up, but most of them are vague, with no real basis to the claims made - most ofcourse say that skipping gears is not an issue. Some of them are brand-specific forums eg. there was this Honda forum where they are discussing Honda's suggestion that gears should not be skipped since they can damage the syncro-rings. And a poster responding that it is because the synchro-rings from Honda are bad in quality etc. Will surely post if I find something credible.