Jerkiness when shifting

[dkstz]

I was wondering if there's a sure way to remove the "jerk" that happens sometimes when shifting geras (in manual cars)...
It's like a little "punch"... it happens a lot with my mom driving, and less to me, but no idea. It's not natural right?
It got something to do with "rev matching"?? By the way, what exactly is that?

Thanks in advance..

 

[///M-Spec]

Practice, practice, practice.

Rev matching = using the throttle to approixmate RPMs of output shaft to equal the input shaft. Most street cars are designed with heavy flywheels that make this easy to master. Downshifts should be accompanied by the light "blip" of the throttle so that RPMs rise before engaging the next (lower) gear.


M

 

[G.T]

My Dad pretty much has the "non-jerkeyness" while shifting down to a tea. You can hardly notice the gear changes sometimes, he's that good (except in hard driving ). Meanwhile, my Uncle really does jerk the car while he changes gear. I'll have to ask my Dad exactly how he does it (not any more, he has an auto now ).

 

[Freddie]

Like M-Spec said. Plus, you can lift the throttle when shifting up to reduce the torque the engine is transmitting, making the shift smoother (automatics work this or in a similar way). The most optimal would of course be rev-matching, because besides being smooth also has the advantage of saving wear on the clutch.

 

[sicbeing]

I've been experimenting with this myself. I just bought my first manual transmission car 2 weeks ago, and I'm doing a lot better.

At first it seemend no matter what I would "buck" the car when shifting, but it seemed that SOMETIMES it wouldn't... so I'm figuring out how to have it not "buck" and find out what's happening when it does work right...

What I've found out so far is shfiting at certain RPMs when cruising helps. If I'm in first, I'll shift into 2nd at around 2500 or 3000 RPMs, and then keep the RPMs around 1500 or 2000 when letting go of the clutch in 2nd gear. Then I'll shift at 2000 again to get into 3rd. This has so far been eliminating any "gear changing resistance" so far that I once thought I had a problem with, and keeping the RPMs at a certain point when letting go of the clutch helps get rid of the car "bucking" foward.

There is a "friction point" I've found when letting go of the clutch, the point where it grabs enough to completly let go of the clutch, no longer having to slowly let go of it. I used to think that no matter what, in 1st gear you have to have the clutch in at least somewhat in order to move. Now I know that isn't true, and I can let the clutch go at the friction point, and the closer I am to 1500 RPMs in 1st, the less (if any at all) "bucking" I have.

It also seems that way in most gears depending on how fast you're going. If you're shifting early, like say in my car going 30MPH and going into 4th is early, then you want to be at a low RPM because when you get into 4th, your car doesn't need a lot of power to move. But say you shifted late, like if you were floring it (or racing) you would need to have the RPMs much higher before you reached the friction point when letting go of the clutch, like say if you're going 35 MPH in 1st then shifting to 2nd.

Hope that helps.

 

[stumpydino]

well jeez it aint that hard iv been on manual since i started last december and i can do it fairly smooth alright as long as you can keep the movements of the pedals in harmony it aint much problem just practice and concentrate on it a lot

 

[Wolfe]

Plus, you can lift the throttle when shifting up to reduce the torque the engine is transmitting, making the shift smoother.

Um...since when is that a "can," as opposed to a "should"...?

No offense to you, since you obviously already know about it, but anyone who hasn't been taught to let off of the throttle when upshifting hasn't been taught properly...

I personally consider my gear-shifting to be both quite quick and almost-unnoticably-smooth...What it all comes down to is smooth, restrained clutch control. I'll describe the technique that seems to work the best for me (which I've tried successfully on several cars and trucks of various origins and ages):

Imagine that the clutch all the way "up" (off of the floor) is 0%, and that all the way "down" (on the floor) is 100%. When upshifting, take your foot off of the accelerator (as I said before, this should be a natural part of your manual-tranny technique), put in the clutch most of the way, if not all (75% - 100%, and this depends on the age/wear of the clutch), select the next gear, quickly pull back your clutch leg most of the way (to somewhere around 25%-10%), and then finish off the rest of that 25%-10% more slowly, while simultaneously applying the first 10%-25% of throttle (the final clutch motion and first throttle motion should be a direct "trade"). As soon as the clutch reaches 0%, do with the throttle as you please.

If done correctly and quickly enough, the engine will slow down to just about the perfect RPM, and the shift will be smooth.

For downshifts, sometimes it's effective enough to simply leave your throttle foot in the same place while you shift. When you put the clutch in, the RPMs will rise, and hopefully match the correct RPM. Also, if you have time, and are just coasting, you can hold the clutch in for a while, and modulate the throttle until it "sounds" like you're in the ballpark, and then let out the clutch and, well...see if you were right.

These techniques are most useful for ordinary day-to-day driving...upshifting in racing usually has nothing to do with smoothness, and downshifting is done with heel-toe, which is more complicated than I feel like explaining right now....

Edit: Oh yeah, and I almost forgot to mention...practice, practice, practice, practice, practice, practice, practice, practice, practice....

 

[dkstz]

wow.. thanks for all those quick answers...
Now I see why and what should I do! gonna try it right now
👍