High RPM clutch drag

[Rope-Pusher]

When all else fails, blame it on the nut that holds the steering wheel.

[Rope-Pusher]

When all else fails, blame it on the nut that holds the steering wheel.

[Rope-Pusher]

High rpm crank-flexing makes the flywheel and clutch cover assembly rotate with a wobble. The wobble is accentuated the further away from the rear main bearing you go. This wobble leads to contact between the flywheel and/or pressure plate and the clutch disk and tries to drag it along at engine speed.

[daleadbull]

High rpm crank-flexing makes the flywheel and clutch cover assembly rotate with a wobble. The wobble is accentuated the further away from the rear main bearing you go. This wobble leads to contact between the flywheel and/or pressure plate and the clutch disk and tries to drag it along at engine speed.

This is what I think I meant when I said look the mounts. Stiffer engine/transmission mounts would help in this case, wouldn't it?

[Rope-Pusher]

High rpm crank-flexing makes the flywheel and clutch cover assembly rotate with a wobble. The wobble is accentuated the further away from the rear main bearing you go. This wobble leads to contact between the flywheel and/or pressure plate and the clutch disk and tries to drag it along at engine speed.

This is what I think I meant when I said look the mounts. Stiffer engine/transmission mounts would help in this case, wouldn't it?

No, crankshaft bending isn't the same as the powertrain moving around underhood. It is due to the thrust of the pistons, through the connecting rods, flexing the crankshaft.

[daleadbull]

High rpm crank-flexing makes the flywheel and clutch cover assembly rotate with a wobble. The wobble is accentuated the further away from the rear main bearing you go. This wobble leads to contact between the flywheel and/or pressure plate and the clutch disk and tries to drag it along at engine speed.

This is what I think I meant when I said look the mounts. Stiffer engine/transmission mounts would help in this case, wouldn't it?

No, crankshaft bending isn't the same as the powertrain moving around underhood. It is due to the thrust of the pistons, through the connecting rods, flexing the crankshaft.

Is that really a concern in today's engines especially in a lower powered production car?

[ClutchFork]

High rpm crank-flexing makes the flywheel and clutch cover assembly rotate with a wobble. The wobble is accentuated the further away from the rear main bearing you go. This wobble leads to contact between the flywheel and/or pressure plate and the clutch disk and tries to drag it along at engine speed.

All else equal, a greater number of main bearings would reduce this. I recall the old inline six-bangers used to have 4 mains, but then some were upgraded to 7 mains. Of course those engines never ran that high of rpm for it to matter much. Also a forged steel crank (rings like a bell when thwacked with a wrench while sitting on carpet) would be better than a cast iron crank (makes a dull thunk when thwacked with a wrench).

[bk7794]

When all else fails, blame it on the nut that holds the steering wheel.

This?

[theholycow]

Not sure if question is serious, but Rope meant this:

[Rope-Pusher]

Not sure if question is serious, but Rope meant this:

You're likin' that decoder ring I sentcha.

[bk7794]

Not sure if question is serious, but Rope meant this:

You're likin' that decoder ring I sentcha.

So the other day I decided to take it up to around 5k in first gear. I then tried shifting it into second and it went in somewhat easily. One thing I hate about that is then I botch the shift going into second because I'm so dead set on trying to determine how the shifter feels lol.

[SonicHKS]

lol @ all the noobs in this thread. bk's problem is actually very simple.

bk, your clutch isn't fully disengaging. Its like you're partially shifting without using the clutch. The problem is worst shifting to 2nd at high rpm in 1st because that has the biggest gap between gears of any shift in that car. Also, if you're trying to shift fast it'll make it worse as you're not rev-matching the shift. Waiting at the gate for 2nd and going in at the right time should revmatch it and have it shift smoothly. You're not having a problem with it in the other gears because in those gears you shift slow enough for it to just revmatch on its own with your normal timing.

Also, another thing. What you're referring to as "clutch engagement" isn't what you think it is. You're referring to it as a point. Its not a point, its an area in the clutch pedal's range of motion. And that area/range will increase as your clutch wears. If the clutch pedal has a range of motion of about 12", ideally you'd want it to grab and fully hookup over an area of an inch or two, and starting at least an inch or 2 off the floor to have some breathing room for clutch disengagement. If your clutch starts to grab "beneath the floor" like you've said, and doesn't fully hook up til high in pedal travel, you're wearing it pretty bad. If anything you've got a glazed clutch, if not one that's on its way out. For one thing the 'not fully disengaging' problem you're having isn't good for a clutch.


Time to go off-topic from your problem. 1st-2nd is a tricky shift for a lot of cars. The Sonic forums have a lot of people who complain about it. Supposedly, the Sonic has a notchy 2nd gear that doesn't like to engage with a high-rpm shift from 1st. Me....I've never had a problem with it. You just have to realize, that's the biggest gap between gears, and you have to give the synchro an extra split second to do its thing. So to me, shifting my Sonic to 2nd at high rpm is actually smoother than low-RPM. At low-rpm its more complicated, a combination of the big gap between gears and the right speed/timing required to get it right. High-RPM its just a fast shift with an extra split second waiting at the gate for 2nd gear.

[Shadow]

Time to go off-topic from your problem. 1st-2nd is a tricky shift for a lot of cars. The Sonic forums have a lot of people who complain about it. Supposedly, the Sonic has a notchy 2nd gear that doesn't like to engage with a high-rpm shift from 1st. Me....I've never had a problem with it. You just have to realize, that's the biggest gap between gears, and you have to give the synchro an extra split second to do its thing. So to me, shifting my Sonic to 2nd at high rpm is actually smoother than low-RPM. At low-rpm its more complicated, a combination of the big gap between gears and the right speed/timing required to get it right. High-RPM its just a fast shift with an extra split second waiting at the gate for 2nd gear.

A "notchy" shift from 1st gear to 2nd gear simply means that the sychronizer isn't up to the job of, well, synchronizing shaft speeds. Why that happens isn't always easily apparent. In some cases, cold temps magnify the issue, mostly because of the viscosity of the gear lube in the box. In other cases, it could be a case of a worn synchro itself. And in other cases, the synchro may be in good condition, but it's just not designed robust enough to effectively do its job properly under all circumstances. Either way, no driver should be forced to compensate by purposely shifting at a specific RPM to avoid a notchy shift. Sure, that may be an easy way to minimize the issue, but a better option is to correct the issue in the first place so you have the freedom and ability to shift at any RPM without getting a notchy shift in the first place.

One thing that can help a great deal (and sometimes completely eliminate notchy shifts) is a simple swap of the gear lube. For example, Redline makes some great products that have been known to completely eliminate notchy shifts. You should try them yourself and maybe then you won't have to run your engine to high RPM in 1st gear all the time to get a smooth shift into 2nd. And you won't have to delay your shift either. I don't want the gearbox telling me how to drive the car; I want to tell the gearbox how I'm going to drive the car. That's the whole point in driving a manual transmission car in the first place.

[bk7794]

I've got a funny issue. The only thing I can guess is that it has something to do with the pitch of the car. When I first start my car in the morning. I go up a slight grade and both the 91 and 00 shift fine into 2nd. Then I come to the end of my street, when I turn right I go downhill, both of the cars definitely do feel notchy only when I go down that hill in the cold weather. Must be the oil sloshing to one side of the transmission. Kind of a funny issue.

Time to go off-topic from your problem. 1st-2nd is a tricky shift for a lot of cars. The Sonic forums have a lot of people who complain about it. Supposedly, the Sonic has a notchy 2nd gear that doesn't like to engage with a high-rpm shift from 1st. Me....I've never had a problem with it. You just have to realize, that's the biggest gap between gears, and you have to give the synchro an extra split second to do its thing. So to me, shifting my Sonic to 2nd at high rpm is actually smoother than low-RPM. At low-rpm its more complicated, a combination of the big gap between gears and the right speed/timing required to get it right. High-RPM its just a fast shift with an extra split second waiting at the gate for 2nd gear.

A "notchy" shift from 1st gear to 2nd gear simply means that the sychronizer isn't up to the job of, well, synchronizing shaft speeds. Why that happens isn't always easily apparent. In some cases, cold temps magnify the issue, mostly because of the viscosity of the gear lube in the box. In other cases, it could be a case of a worn synchro itself. And in other cases, the synchro may be in good condition, but it's just not designed robust enough to effectively do its job properly under all circumstances. Either way, no driver should be forced to compensate by purposely shifting at a specific RPM to avoid a notchy shift. Sure, that may be an easy way to minimize the issue, but a better option is to correct the issue in the first place so you have the freedom and ability to shift at any RPM without getting a notchy shift in the first place.

One thing that can help a great deal (and sometimes completely eliminate notchy shifts) is a simple swap of the gear lube. For example, Redline makes some great products that have been known to completely eliminate notchy shifts. You should try them yourself and maybe then you won't have to run your engine to high RPM in 1st gear all the time to get a smooth shift into 2nd. And you won't have to delay your shift either. I don't want the gearbox telling me how to drive the car; I want to tell the gearbox how I'm going to drive the car. That's the whole point in driving a manual transmission car in the first place.

Have you heard of something called shift blocking?

http://en.wikipedia.org/wiki/Shift_blocking

I wondered what your opinion was. This is actually brand new to me.

lol @ all the noobs in this thread. bk's problem is actually very simple.

bk, your clutch isn't fully disengaging. Its like you're partially shifting without using the clutch. The problem is worst shifting to 2nd at high rpm in 1st because that has the biggest gap between gears of any shift in that car. Also, if you're trying to shift fast it'll make it worse as you're not rev-matching the shift. Waiting at the gate for 2nd and going in at the right time should revmatch it and have it shift smoothly. You're not having a problem with it in the other gears because in those gears you shift slow enough for it to just revmatch on its own with your normal timing.

Also, another thing. What you're referring to as "clutch engagement" isn't what you think it is. You're referring to it as a point. Its not a point, its an area in the clutch pedal's range of motion. And that area/range will increase as your clutch wears. If the clutch pedal has a range of motion of about 12", ideally you'd want it to grab and fully hookup over an area of an inch or two, and starting at least an inch or 2 off the floor to have some breathing room for clutch disengagement. If your clutch starts to grab "beneath the floor" like you've said, and doesn't fully hook up til high in pedal travel, you're wearing it pretty bad. If anything you've got a glazed clutch, if not one that's on its way out. For one thing the 'not fully disengaging' problem you're having isn't good for a clutch.


Time to go off-topic from your problem. 1st-2nd is a tricky shift for a lot of cars. The Sonic forums have a lot of people who complain about it. Supposedly, the Sonic has a notchy 2nd gear that doesn't like to engage with a high-rpm shift from 1st. Me....I've never had a problem with it. You just have to realize, that's the biggest gap between gears, and you have to give the synchro an extra split second to do its thing. So to me, shifting my Sonic to 2nd at high rpm is actually smoother than low-RPM. At low-rpm its more complicated, a combination of the big gap between gears and the right speed/timing required to get it right. High-RPM its just a fast shift with an extra split second waiting at the gate for 2nd gear.

Keep in mind the high engagement is on a cable clutch. One adjustment and you can move the engagement point down. Then again you get lousy pedal feel. But when you're trying to get as much life out of the clutch as possible, who cares. I'm wondering about the clutch in my 00. With it being a used car I have no idea on how the car was treated, the clutch and all that. I must admit I'm sure the transmission wasn't treated all too well with Reverse having some problems engaging. It all works now and I just like having the peace of mind knowing I can get into 2nd if I am in a hurry.

[tankinbeans]

If I were forced to shift that way I'd have to break something. As Clarkson would say, "I'm the driver, I know what gear I want, not you. You silly thing, you."

I skip shift all the time, but that's by choice not some farsical automotive engineering "feature".