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Old 09-30-2007, 02:51 PM   #1
tig
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downshifting from 5th gear staight to 3rd

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.
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Old 09-30-2007, 03:18 PM   #2
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It's fine as long as you don't do it at 140km/h.
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Old 09-30-2007, 03:19 PM   #3
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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).
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Old 09-30-2007, 03:55 PM   #4
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Quote:
Originally Posted by 328DTM View Post
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!!
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Old 09-30-2007, 03:20 PM   #5
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it's okay, but anytime you skip gears you'll put wear on your syncros.
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Old 09-30-2007, 04:46 PM   #6
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Quote:
Originally Posted by Soldo View Post
it's okay, but anytime you skip gears you'll put wear on your syncros.
Not if you double clutch with your rev-match. And you put wear on your synchros with any downshift if you don't double clutch.
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Old 09-30-2007, 06:07 PM   #7
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Not if you double clutch with your rev-match. 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
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Old 09-30-2007, 06:16 PM   #8
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Quote:
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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.
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Old 09-30-2007, 06:05 PM   #9
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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
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Old 09-30-2007, 08:59 PM   #10
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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.
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Old 09-30-2007, 09:07 PM   #11
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Originally Posted by T.Dot_E30 View Post
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!?
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Old 09-30-2007, 09:41 PM   #12
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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.
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Old 10-01-2007, 08:29 AM   #13
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Originally Posted by T.Dot_E30 View Post
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.
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Old 09-30-2007, 06:52 PM   #14
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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.
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Old 09-30-2007, 06:57 PM   #15
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i go from 5th to 3rd all the time.. nothing wrong with that, just rev match it
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