Hey,
07' has 1900 miles. I took it on my first several hundred mile journey today so it was the first time I shifted b/w 6th and 5th on the interstate alot. I came up behind a slower car so I shifted to 5th then just let out on the clutch w/o adding throttle (sort of coasting after the downshift). When the car ahead got a little distance from me, I eased back on the throttle and that's when I felt a distinct "jerk" from I assume the transmission. The jerk was easy to reproduce on a downshift in 5th and 4th gear if I just let out on the clutch and delayed giving throttle. I could not however reproduce the jerk on an upshift (i.e. Upshift, let all the way out on clutch, then add throttle).
Its probably normal, just a little "slack" take up from coasting but I have never noticed it an any other manual trany I have driven...
Any thoughts?
Just to clarify.....
When you shift from 6th to 5th or from 5th to 4th WITHOUT rev matching you get a pull or jerk from the transmission? I believe that this is perfectly normal.
You need to blip the throttle so that the engine speed matches the gear and this will get rid of any jerks. Doesn't happen when you are going up through the gears cos the engine revs are dropping with each new gear.
But at 75mph in 3rd your rpms are about 5000.
75mph in 2nd your rpms are about 7000.
If you downshift from 3rd into 2nd(you never would but for the sake of this say you do) at 75mph without rev matching your 2nd gear is 2000rpm short of how fast it has to rotate at that speed. Without rev matching two things will happen rarther violently.
1. Your revs will shoot upwards.
2. You will decrease rapidly.
You'll also get a new and interesting smell called 'expensive' as the clutch takes the abuse.
So blip the throttle and THEN downsift with the revs now matching the gear that you are selecting. This is not heel and toeing unless you need to brake at the same time, in which case the old 'two feet, three pedals' problem rears its ugly head. For a standard downshift without braking its just.....
1. Foot on the clutch.
2. Blip of the throttle.
3. Select the lower gear while the revs are still high.
4. Reengage the clutch.
If you need to know how to heel-toe then there is currently an argument rarging somewhere else on thses forums on the best way to do it, so have at over there for that information.
If what you are experiencing is something else then please disregard this completely.
Gmorat.
Gmorat,
Thanks for the reply and the info. I also ride sport bikes so I have a pretty good understanding of the rev match. And of course, I will be honest with you, given that I have been trying my best to adhere to the break in period, my 6th to 5th downshifts have been at <3.5K and at that RPM they are smooth no matter how you do it. My possible problem takes place after all of that. After reengaging the clutch slowly after the rev match, my foot now off the clutch and throttle, instead of getting back on the throttle as you would normally do, if I let the car "coast" for a second or two, then ease back on the throttle, I get a very distinct jerk before I get acceleration as if there is slack somewhere. Thanks for any additional comments and I agree, well said on the rev match.
Larry
Hey.
I think I know what your talking about and the trick is be much more positive on your throttle. I find that if I am being over-careful the car can feel jerky. Try getting on the throttle sooner and see if that helps. Don't allow that period of just the car in gear but no throttle and if using the inertia of the engine to slow the car then just ease off the gas afterwards if your trying to engine brake.
A question for you. I was talking to a guy who drives bikes and he mentioned offhandedly that bikes are unstable unless you are using the throttle because its the torque in the wheels that keep them upright. Can you explain what he was talking about as I may have picked it up wrong and it sounds pretty alien to a four wheeler like me.
G.
Hey,
Your are exactly right, it doesn't do it at all when I do a normal downshift (i.e. get right back on the throttle after reengagement of the clutch). I just so happen to notice this the first time when I downshifted for a slower car on the interstate and was close enough to the car that couldn't get back on the throttle right away. Never noticed this in any other trany I have driven.
It is at this point, however, a run-her-and-watch-her problem as everything else is smooth as silk.
As far as the motorcycle goes, it is more the forward momentum that the throttle gives you that keeps the bike up than the throttle itself. That is why, for example, it is easier to take your hands off the handlebars the faster you are going. It's physics, but basically the more momentum you have in one direction, the more force it takes to change that direction, thus increased stability. Thanks for the help.
Larry
In a nutshell, the bike stays up because there are two big gyroscopes trying to keep it that way. If you want details, I am the wrong guy.
Marty
