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View Full Version : downshifting from 5th gear staight to 3rd


tig
09-30-2007, 02:51 PM
me and my buddy have been arguing about this for a while now. how bad is it to downshift from 5th gear staight to 3rd, i have done it a couple of times on the highway when i m down just under 100km/h at about 2.5rpm i find that if i drop it down to 3rd in my e36 328, it has greattt pickup engine revs up to about
3500 rpm and until about 6000rpm the car fliess, i have only done it a couple of times once when going up against a S4, i dont speed too much cuz i dont want my license getting suspended by these stupid new laws, anyways i know this cant me good for the engine i know anytime the engine revs too high its not good for it, but how bad is dropping straight to 3rd from 5th for the cars tanny? my buddy says its horrible for the car i say it cant be good but i dont think its horrible.

mirek
09-30-2007, 03:18 PM
It's fine as long as you don't do it at 140km/h.

330DTM
09-30-2007, 03:19 PM
If you want a smooth transition just rev match from 5th into 3rd (not hard to do). If you don't rev match, the transition won't be as smooth, especially if you're getting ready to 'run' against someone, cause you're going to feel the car jolt as you clutch out quickly (without rev matching).

Soldo
09-30-2007, 03:20 PM
it's okay, but anytime you skip gears you'll put wear on your syncros.

v_bimmer
09-30-2007, 03:55 PM
If you want a smooth transition just rev match from 5th into 3rd (not hard to do). If you don't rev match, the transition won't be as smooth, especially if you're getting ready to 'run' against someone, cause you're going to feel the car jolt as you clutch out quickly (without rev matching).
+++1

as long as you rev match and dont do it at a very high speed its fine!!! and about the engine reving high its fine, as long as you take good care of the engine!!! and its just a car, have fun with it!!

Dr. Flyview
09-30-2007, 04:46 PM
it's okay, but anytime you skip gears you'll put wear on your syncros.

Not if you double clutch with your rev-match. *th-up* And you put wear on your synchros with any downshift if you don't double clutch.

tig
09-30-2007, 06:05 PM
it's okay, but anytime you skip gears you'll put wear on your syncros.

thats exactly what i thought , ya gotta make sure to rev match other wise the shift is not smooth, thanx guys

JMW
09-30-2007, 06:07 PM
Not if you double clutch with your rev-match. *th-up* And you put wear on your synchros with any downshift if you don't double clutch.

we dont need to double clutch our cars...
tey are for tractor trailers and big rigs i believe with no synchros....
the line "not double clutchin like you should" in fast in the furious was a technical term to look cool...but u don need to do it..
i didnt think

Dr. Flyview
09-30-2007, 06:16 PM
we dont need to double clutch our cars...
tey are for tractor trailers and big rigs i believe with no synchros....
the line "not double clutchin like you should" in fast in the furious was a technical term to look cool...but u don need to do it..
i didnt think

Look at what I wrote carefully. Synchros are made so you don't have to double clutch, but if you don't double clutch, you put wear on the synchros.

Soldo
09-30-2007, 06:52 PM
Even if you double clutch your syncro's should still be working. Mind you, the wear you put on your syncros by going from 5th to 3rd isn't anything i'd be extremly worried about.

golden
09-30-2007, 06:57 PM
i go from 5th to 3rd all the time.. nothing wrong with that, just rev match it

Axxe
09-30-2007, 07:00 PM
Why double clutch? The synchro's still spin it up, as long as it's rev matched you're ok.

Boots R
09-30-2007, 07:59 PM
I do it all the time when i'm going 180. I love the sound of valves popping.

dbworld4k
09-30-2007, 08:17 PM
I do it all the time when i'm going 180. I love the sound of valves popping.

LOL!

Meegis
09-30-2007, 08:28 PM
You're all asking the wrong questions....



How did the S4 do?

T.Dot_E30
09-30-2007, 08:59 PM
it's okay, but anytime you skip gears you'll put wear on your syncros.

Its not the skipping gears that does that, its the stress from the tranny having to match the speed of the car by forcing the engine to rev. syncronosing the gears.

Done right, it shouldn't be a problem.

Just don't drop it into second doing 120+, your engine won't like 10k rpm.

Soldo
09-30-2007, 09:07 PM
Its not the skipping gears that does that, its the stress from the tranny having to match the speed of the car by forcing the engine to rev. syncronosing the gears.

Done right, it shouldn't be a problem.

Just don't drop it into second doing 120+, your engine won't like 10k rpm.

You're right! The shop i used to work at told me that, but they said since there isn't much stress when your changing gears accordingly it doesn't wear the syncros.

So lemme ask you this, rev matching still makes the syncros work, right!?

T.Dot_E30
09-30-2007, 09:41 PM
So lemme ask you this, rev matching still makes the syncros work, right!?

They work everytime you change gears,...they just don't have to work as much when the engine speed is close to where it should be.

tig
09-30-2007, 11:43 PM
You're all asking the wrong questions....



How did the S4 do?


lol the s4 driver couldnt drive for shit man, he was beside me, we both took off pretty even but he dropped back by like 4 cars when he changed gears, so thats was it, i hit the brakes after because there was a car infront of me and it seemed to me like the race was done, but the guy in the s4 decided to blow by me like a loser after the race was aleady done, i hate when ppl do that, i m curious to see how i would do against one with a driver that can actually drive, my brother has a 2.8 and i can take that no problem but an S4 should be able to take a 328 with ease right?

BigD
10-01-2007, 08:29 AM
They work everytime you change gears,...they just don't have to work as much when the engine speed is close to where it should be.

The engine speed doesn't matter if you're not double clutching. The syncros are designed to speed up or slow down the input shaft of the transmission, nothing else. They're just cone clutches (usually brass) that help engage the dogs. That's why it's a terrible idea to shift without clutching on syncro gearboxes - if you're off by even a little bit, those little clutches have to slow down or speed up your engine and they are not designed to do that. And if they wear out, you won't be able to get into gear at all. I'd personally love a straight cut non-syncro box in my track car some day.

If you down shift and revmatch, all you do is make the clutch do no work, the syncros won't know the difference. For upshifting, you can make a difference by shifting quickly, so the input shaft only slows down enough to match the new gear speed and the syncro doesn't have to do any work.

INFAMOU$
10-01-2007, 08:44 AM
i shift mine without the clutch all the time.. as long as you rev match you're fine.. It's also a great way to test a transmission when buying a new car.. take it through all the gears without using the clutch.. if it doesn't grind up/down shifts then she's been well taken care of :)

T.Dot_E30
10-01-2007, 08:56 AM
The syncros are designed to speed up or slow down the input shaft of the transmission, nothing else.


Really, so syncros have nothing to do with synchronizing the gears so they mesh cleanly?
:confused:

The input shalf has gears on the end of it, that meshes with the gear you select, which in term meshes with the gears on the output shalf.

We're saying the same thing.

BigD
10-01-2007, 10:30 AM
i shift mine without the clutch all the time.. as long as you rev match you're fine..

No you are not. You will never match the revs perfectly and you are abusing your syncros every time you do this. I know it doesn't feel like it to you but that's because for now, they are helping you out. In time you won't be able to get into gear at all, clutch or not - the same mechanism that is designed to help you engage the gear will prevent you from doing it. The reason you can get away with clutchless shifting on a non-syncro box is because the windows for the dogs on the gears are wider than they need to be to allow some error, and there are no syncros to wear out to fix your inaccuracy.

Really, so syncros have nothing to do with synchronizing the gears so they mesh cleanly?
:confused:

The input shalf has gears on the end of it, that meshes with the gear you select, which in term meshes with the gears on the output shalf.

No they don't and no it doesn't. The gears are always meshed (unless you want to talk about 80 year old transmissions). The only thing the syncros do is syncronize the speed of the half shaft (and lay shaft if you want to get all anal) so the dogs can engage with the already meshed gear.

INFAMOU$
10-01-2007, 11:26 AM
Well I have been shifting my T5 in my mustang for the past 100k with no clutch and still no issues.. I put 80k on my white e36 with no issues.. I only do it when shifting around 3-4k rpm driving conservatively.. I always use the clutch when driving spiritedly. With the abuse they take driving spiritedly they are more likely to blow from missing a gear or the torque before my synchros wear out.. but i know what you're sayin...

T.Dot_E30
10-01-2007, 11:30 AM
No they don't and no it doesn't. The gears are always meshed (unless you want to talk about 80 year old transmissions). The only thing the syncros do is syncronize the speed of the half shaft (and lay shaft if you want to get all anal) so the dogs can engage with the already meshed gear.

No it doesn't as in your telling me this input shalf doesn't have gears on the end of it that mesh with the other gears within the transmission?

I don't see how each gear is always meshed, they are turning at different speeds and would each turn the output shalf at different speeds, when are are not in use I cannot see how they would all be connected, turning the output shalf at the same time. Even if they are, atleast one gear needs to mesh with the selector rod chooses a gear.

http://static.howstuffworks.com/gif/transmission-5speed-gears.gif

propr'one
10-01-2007, 11:33 AM
I'm sure shifting without the clutch does wear your synchro's, however, if you do it well, although you probably wont get it quite bang on, it will be close enough such that it minimizes the wear on your synchro's.

i shift without the clutch every once in a while when i'm too lazy to move my left foot.

BigD
10-01-2007, 11:41 AM
No it doesn't as in your telling me this input shalf doesn't have gears on the end of it that mesh with the other gears within the transmission?

I don't see how each gear is always meshed, they are turning at different speeds and would each turn the output shalf at different speeds, when are are not in use I cannot see how they would all be connected, turning the output shalf at the same time. Even if they are, atleast one gear needs to mesh with the selector rod chooses a gear.

http://static.howstuffworks.com/gif/transmission-5speed-gears.gif

You just posted a diagram showing all gears meshed... I'm not sure what your confusion is. I never said they are turning the output shaft at the same time, please re-read. Engaging a gear and meshing it are not the same thing (since circa 1929).

BigD
10-01-2007, 11:45 AM
I'm sure shifting without the clutch does wear your synchro's, however, if you do it well, although you probably wont get it quite bang on, it will be close enough such that it minimizes the wear on your synchro's.

i shift without the clutch every once in a while when i'm too lazy to move my left foot.

Please don't confuse minimized with minimal. No matter how close you get it, if you're not exactly right, that little difference is not a question of changing the momentum of two relatively small sticks and a clutch disk but rather changing the RPM of an engine. That is a load the syncros were never designed for and they will fail many times faster than if you simply use the clutch and let them do the job they are designed for. It's the difference between a transmission that lasts 500k+ withour a rebuild, and one that doesn't go into gear at 200k.

T.Dot_E30
10-01-2007, 11:46 AM
Just to illustration what i mean.

http://static.howstuffworks.com/gif/transmission-synchronizer.gif

The cone on the blue gear fits into the cone-shaped area in the collar, and friction between the cone and the collar synchronize the collar and the gear. The outer portion of the collar then slides so that the dog teeth can engage the gear.

Every manufacturer implements transmissions and synchros in different ways, but this is the general idea.

T.Dot_E30
10-01-2007, 11:49 AM
You just posted a diagram showing all gears meshed... I'm not sure what your confusion is. I never said they are turning the output shaft at the same time, please re-read. Engaging a gear and meshing it are not the same thing (since circa 1929).

Sorry, I thought engaging meshing was the same thing....but either way engage a gear should need some Synchronizing .

BigD
10-01-2007, 12:00 PM
Sorry, I thought engaging meshing was the same thing....but either way engage a gear should need some Synchronizing .

Right. So going back to where we started, the engine speed has nothing to do with the synchronization process, because what you need to syncronize is the input shaft with the output shaft so the dogs can engage, which is what those little cone clutches do. When the engine comes into play, everything in the gearbox is synchronized and engaged, from here your revmatching skills or lack thereof will only affect the clutch.

T.Dot_E30
10-01-2007, 12:22 PM
Right. So going back to where we started, the engine speed has nothing to do with the synchronization process, because what you need to syncronize is the input shaft with the output shaft so the dogs can engage, which is what those little cone clutches do. When the engine comes into play, everything in the gearbox is synchronized and engaged, from here your revmatching skills or lack thereof will only affect the clutch.

Make sense, I was thinking of something else when you said the gears always being mesh, and not needing synchronizing.

The discrepancy was what needed to be synchronized, not weather it took place.

I was arging it needed to take place, not which gears it took place on.

Fel
10-01-2007, 04:15 PM
Interesting read, I've learned a lot :)

Just a question... funny enough, I was thinking of this this morning. Someone told me a few years ago that they can change gears without using the clutch. I was under the impression that this wasn't possible.

Could someone explain the mechanics of shifting without the clutch? How the hell does that work? Isn't the gear "locked in" until you use the clutch pedal? I'll say I've never done it (and probably won't in fear of leaving my transmission in pieces somewhere on the road behind me), but how...? I'm confused....

Boots R
10-01-2007, 04:22 PM
Interesting read, I've learned a lot :)

Just a question... funny enough, I was thinking of this this morning. Someone told me a few years ago that they can change gears without using the clutch. I was under the impression that this wasn't possible.

Could someone explain the mechanics of shifting without the clutch? How the hell does that work? Isn't the gear "locked in" until you use the clutch pedal? I'll say I've never done it (and probably won't in fear of leaving my transmission in pieces somewhere on the road behind me), but how...? I'm confused....


I used to do it in my old truck. And then the transmission blew.

BigD
10-01-2007, 04:27 PM
Interesting read, I've learned a lot :)

Just a question... funny enough, I was thinking of this this morning. Someone told me a few years ago that they can change gears without using the clutch. I was under the impression that this wasn't possible.

Could someone explain the mechanics of shifting without the clutch? How the hell does that work? Isn't the gear "locked in" until you use the clutch pedal? I'll say I've never done it (and probably won't in fear of leaving my transmission in pieces somewhere on the road behind me), but how...? I'm confused....

There are a lot of very good technical articles about how manual transmissions work, come back with something a little more specific and less time consuming to answer... (yes I know I clearly have a lot of it to spare at the moment but I'm also very lazy :P)