motor

GTO · 08-02-2004, 04:27 AM

Last night I was testing out how to downshift smoothly and found (for instance) if I'm cruising at 70KPH in 4th, I leave the accelerator pedal where it is, engage the clutch and smoothly put it into three and release the clutch in one smooth moment I can get completely unnoticeable gear change into 3rd gear.

I’m sure its called “syncro shifting”.

Basically I want to know, if syncro shifting damages a standard WRX gear box?

Spoke to some people and I get conflicting answers, my view is that; that it’s a modern syncro tranny, since there no sudden change of load, no noise, resulting in an unnoticeable shift it should be ok?

Comments please!!!

blah · 08-02-2004, 04:34 AM

I do the same thing sometimes when i down shift. Usually i just wait for the car to slow down, and just slip it into gear.

stracing · 08-02-2004, 07:35 AM

i got reports that it hurts your tranny

so i heel toe everytime. or rev the engine to go for the lower gear when i want move a bit quicker.

mindgam3 · 08-02-2004, 08:44 AM

When you put the clutch down, your revs will instantly drop and your crank speed wont be matching your cars speed for that particular gear. When you re-engage the clutch in a lower gear, the engine has to go from next to no revs up to many revs in a relatively short space of time which im guessing could damage the transmission but im not sure. By heel and toeing, you match the engine speed with the transmission speed so there is less of a speed difference when you re-engage the clutch.

Vansquish · 08-02-2004, 01:52 PM

I think you missed part of the post guys...he said he left the accelerator where it is...in other words, it was partly pressed when he put the clutch in...if that was the case, he was in essence doing the same thing as a heel-and-toe downshift, but merely left out the brake usage. In such a case it doesn't hurt your transmission except for the usual wear and tear of shifting. The more shifts you complete over the lifetime of the car, the more frequently you'll have to replace the clutch and so forth...but even that might last the whole time, my mom's got a V6 manual Ford Contour (mondeo for the rest of the world) and it's got 115,000 miles and has the original clutch.

My understanding of "synchro-shifting" (though it may well be wrong) is that in fact you leave the clutch out of the equation entirely. In a modern vehicle with synchromesh equipped transmission, you can actually upshift and downshift without using the clutch. You merely take the lever, push towards the gear you wish to be in and apply steady but not too heavy pressure. If you do it right and manage to find the right engine speed, the lever will pop right into place after the synchros match the gearbox to the engine speed. THAT is not a good thing to do, as it does do damage, however that doesnt' mean that it's not possible.

T-Bird · 08-02-2004, 02:03 PM

yes Syncro means that it syncronizes the speeds at the shafts and in essence makes shifting smoother but you still have to use the clutch if you plan on keeping the transmission for a while.

jon_s · 08-02-2004, 02:42 PM

I always understood synchro-shifting to be the same as Vanquish described.

T-Bird · 08-02-2004, 02:52 PM

yes that is correct but it's not all there is to the equation you have to use the clutch when you shift unless you want the damn thing to go out on you a few years down the road or sooner if you never use the clutch. when you're hauling down the road you want to use the clutch, you can leave out the clutch but not entirely and not all the time, not using the clutch is like PowerShifting. Most cars that have a manual if not all new have Syncro-Mesh Gear Boxes which makes the shifts smoother and essentially quicker. If you ever drove like a car from the 60's or later you might hear them make some grinding noises when shifting especially really old cars from before the 50's that was because you had to force the teeth to catch eachother.

mindgam3 · 08-02-2004, 03:27 PM

When shifting normally then, would you say u had to depress the clutch fully whilst changing gear? or does it not matter how much you depress the clutch pedal as long as u do so?

jon_s · 08-02-2004, 04:15 PM

You don't have to fully depress the clutch. Every car is differenct, but when the clutch is disengaged then that is it. One way of finding this point is by driving along at say 30mph on a straight road. slowly depress the clutch and when the revs start to increase is the point when the clutch is out. Learn where this point is (go a little further to be sure) and you can change gear without depressing the clutch all the way.

However, when I am on a track the clutch motion happens so quick that I doubt there is any real advantage over doing the above. again this depends on the car, as mine has a relatively short distance to go through, some cars have a huge motion on the clutch, so then perhaps there is an advantage.

Vansquish · 08-02-2004, 04:43 PM

You only need to depress the clutch enough so that it "bites". That is the point at which the clutch meshes and the engine and transmission begin operating as a single entity. To shift, you need to go slightly beyond that point so that the two are disconnected for a moment and then let the clutch back out, if you don't do that, you're "synchro-shifting" and in essence forcing the gearchange to occur against the will of the transmission.

Sachmo12345 · 08-02-2004, 05:34 PM

what if i put the clutch in and then rev it up and shift into a lower gear is that basically the same thing

Vansquish · 08-02-2004, 05:39 PM

yeah, that's just matching revs to the gears...it's perfectly allowable...the only thing you'll end up doing is burning more gas that way hehe.

mindgam3 · 08-02-2004, 05:46 PM

Originally Posted by jon_s

You don't have to fully depress the clutch. Every car is differenct, but when the clutch is disengaged then that is it. One way of finding this point is by driving along at say 30mph on a straight road. slowly depress the clutch and when the revs start to increase is the point when the clutch is out. Learn where this point is (go a little further to be sure) and you can change gear without depressing the clutch all the way.

However, when I am on a track the clutch motion happens so quick that I doubt there is any real advantage over doing the above. again this depends on the car, as mine has a relatively short distance to go through, some cars have a huge motion on the clutch, so then perhaps there is an advantage.

hehe thats what i thought, thanks for confirming that though

mit5005 · 08-02-2004, 06:42 PM

Originally Posted by T-Bird

yes that is correct but it's not all there is to the equation you have to use the clutch when you shift unless you want the damn thing to go out on you a few years down the road or sooner if you never use the clutch. when you're hauling down the road you want to use the clutch, you can leave out the clutch but not entirely and not all the time, not using the clutch is like PowerShifting. Most cars that have a manual if not all new have Syncro-Mesh Gear Boxes which makes the shifts smoother and essentially quicker. If you ever drove like a car from the 60's or later you might hear them make some grinding noises when shifting especially really old cars from before the 50's that was because you had to force the teeth to catch eachother.

I have always heard that if you have an old car that doesn't have a synchronized trans, it is best to double clutch. Am I right?