stuck caliper...

Caroline wrote:
> "jim beam" > wrote
>
>>Caroline wrote:
>>
>>>"jim beam" > wrote
>>>
>>>
>>>>Abeness wrote:
>>>>
>>>>
>>>>>TeGGer® wrote:
>>>>>
>>>>>
>>>>>>"Downshifting" without double-clutching is not smart. You are NOT
>>>>>>supposed to use the clutch as a brake pad.
>>>>>>
>>>>>>Downshift properly and there is zero wear on the friction disc.
>>>>>
>>>>>
>>>>>I've heard here that double-clutching means putting it in neutral
>>>>>between shifts and letting the clutch out (i.e., releasing the pedal),
>>>>>but wouldn't the point be to simply rev-match (approximately, after long
>>>>>experience) before engaging at the lower gear, to reduce the wear on the
>>>>>clutch?
>>>>
>>>>there's no real wear on the clutch from shifting, whether just relying
>>>>on synchros or double clutching. clutch wear comes from drive-away from
>>>>a standstill, holding it on the clutch on hills, "resting" a foot on the
>>>>clutch pedal on the freeway, etc. if you don't peel away from lights,
>>>>use the parking brake on hills & rest your foot on the floor, there's no
>>>>reason a clutch won't last like tegger's is doing. also don't under
>>>>rate a dealer's hunger for recommending unnecessary work.
>>>
>>>
>>>Before I saw Jim's post and mention of the "synchro," I was torn about
>>>
>>>1. wear on clutches from shifting
>>>2. the need to double-clutch
>>>
>>>Speaking as someone who's never "DIY replaced" a clutch, the "synchro"
>
> piqued my
>
>>>interest. The reports I am seeing say that modern synchros (about the last
>>>twenty years or so?) preclude the need to double clutch (as many of you I'm
>
> sure
>
>>>have heard). For example:
>>
>>changing a clutch is a procedural pita because of access, but it's not
>>technically hard. the cam belt is technically much more involved even
>>though access is much easier.
>
>
> I'm just figuring I'm going to need some kind of hoist to do it right. (Maybe
> I'm wrong. I studied what you said before and the manual on this.) Not sure I'll
> feel so inspired to go spend some serious bucks on something I think I will only
> use once every say 15 years.
>
>
>>>1.
>>>"In modern cars double-clutching is replaced by a synchronizer."
>>>http://www.angelfire.com/hiphop3/ppd.../ManTrans.html
>>>
>>>2.
>>>"Manual transmissions in modern passenger cars use synchronizers to
>
> eliminate
>
>>>the need for double-clutching."
>
> http://auto.howstuffworks.com/transmission6.htm
>
>>>3.
>>>"Today, all manual transmissions have 'synchros,' so double clutching is
>>>completely unnecessary. And in fact, it DOES put extra wear and tear on the
>>>clutch because you're using it twice for every shift instead of once."
>>>http://www.cartalk.com/content/colum...cember/11.html
>>>
>>>4.
>>>" 'Synchronizers' in manual transmissions in modern passenger cars,
>
> eliminate
>
>>>the need for double-clutching."
>
> http://www.automotiveforchicks.com/?page=tips
>
>>hmm, automotiveforchicks propagating old lore about the 3000 mile oil
>>change & changing transmission fluid "every 100,000 kms or 32,500 miles"
>>has got to challenge their credibility.
>
>
> Aside: They called this a rule of thumb. In closing on this, the site says:
> "Bottom line: Maintain the practice of changing engine oil at recommended
> intervals."
>
> I'm not saying any of the above sites are perfect. I am saying there does seem
> to be a consensus re synchros greatly improving clutch life and performance
> (probably performance was the bigger motivation, as far as I can tell). That's
> why someone thought of the synchro, right?
>
>
>>>I did see some arguments (one?) about using double clutching to spare wear
>
> on
>
>>>the synchro. OTOH, the synchro might be something that lasts the life of a
>
> car.
>
>>>I didn't quite get resolution on this.
>>
>>generally, synchros do last the life of the car. some of the old types
>>of synchro, notably some of the early porsche designs, were great for
>>racing & fast forced shifts, but they wore quickly, particularly if
>>there were problems with insufficient clutch disengagement [clutch plate
>>not being sufficiently free to "float" on the drive pinion], then they'd
>>check out pretty darned quick. the current cone clutch design of
>>synchro just shrugs off bulk abuse.
>>
>>if you want a conclusive demo on the value of synchros/double-clutching,
>>drive something like a cement truck.
>
>
> My 1.5 liter, under two ton Civic is not a cement truck, so I see your point but
> am not sure this would say anything terribly meaningful... Very different
> engineering and needs being satisfied...

but caroline, you're an engineer. example of extreme is meant to
illustrate the principle. braking in neutral is pretty generally
inconsequential in a car, but very very dangerous in a truck. the value
of synchros in a car, especially to a driver that may never have tried
anything without them, is, imo, not appreciated until a different kind
of vehicle is experienced. a big truck, where synchros merely assist,
not override the gear change procedure, is easier/better experience to
get than finding some old stick-shifting banger with straight cut gears.

>
>
>>>At the moment I am under the impression that the really big wear item in,
>
> say,
>
>>>circa 1988-1995 Civics with manual transmissions (which seems to include my
>
> 91
>
>>>Civic and possibly going back a few years more) may be the clutch release
>>>bearing. It wears with every depress-and-release of the clutch pedal. Also
>>>riding the clutch pedal between shifts or keeping it depressed at stops will
>>>wear it.
>>
>>the thrust bearing should last at least the life of the clutch. if a
>>clutch is badly adjusted or the driver "rides" the clutch pedal all the
>>time, it will wear more quickly, but i wouldn't worry about it. you've
>>got this far, so i doubt your driving habits are bad.
>
>
> Aside: I'd like to see more reports from others here who have had clutch parts
> replaced.

most shops just replace everything - clutch, pressure plate, thrust
bearing, pilot bearing, and often skim the flywheel too. personally,
i'm happy just replacing the clutch plate if everything else is ok. if
the flywheel is skimmed, the bolt mounting surface needs to be skimmed
also to maintain the same degree if differential with the friction
surface that it had when new. frequently, that's not done so people
wonder why the clutch goes again so soon again after... insufficient
pressure can be brought by the pressure plate.

>
>
>>>I am still a little intrigued about the argument that 'the clutch is being
>
> used
>
>>>as a brake pad when one downshifts.' Seems to me that engine inertia is
>
> being
>
>>>used as a brake pad, and engines are iron horses that can take it for a
>
> design
>
>>>life of say 15 years and 250k miles plus..
>>
>>correct, it's the engine that does the braking, not the clutch.
>>
>>
>>>For now, I suppose the real argument
>>>against downshifting as a means of slowing the car down is that many, when
>>>downshifting from 5th gear to 1st to neutral, will use the clutch say five
>>>times. Compare this to shifting from 5th to neutal and using the disc/drum
>>>brakes on the wheels; the clutch is used once. Downshifting translates to
>
> using
>
>>>the release bearing several times more each time the car comes to a stop.
>>
>>shifting down through the gears is not that big a deal. consider the
>>principle of the relative loads; can you "chirp" the drive wheels
>>downshifting? no? then there's not as much load as chirping on the
>>up-shift.
>
>
> What is the meaning of the (I suspect highly technical) term "chirp"?

on the change up from 1-2, [& 2-3 if you have a powerful motor], floor
the gas, then slam the clutch into the gear. it'll "chirp" the wheels
as they spin momentarily with the engine's momentum. it's an immaturity
thing.

>
>
>>you don't "need" to go 5-4-3-2-1 by the way. 5-3-1 is perfectly ok.
>
>
> Yes, I do this often. Just depends on the situation. I think over the years I
> have come to operate by what has perhaps become fortuitous feel. In general, I
> avoid letting the engine spike high or low in RPMS all of a sudden.
>
>
>>braking in neutral is potentially very dangerous. not only are you in
>>no position to apply power if required, you also have no engine braking.
>
>
> Ha. Interesting point.
>
> Plus, maybe here or somewhere else on the net I read recently it's illegal in
> many areas to let the car coast (say to a stop) in neutral, for the reason you
> give.
>
>
>> again, going back to the cement truck, losing brakes on a fully loaded
>>vehicle because they've overheated on a big descent is no joke. trust
>>me on that. engine braking may not be "necessary" in all situations,
>>but to get out of the habit is a big no-no.
>
>
> I should toss in at this point that Tom 'n' Ray, despite their comments above,
> say not to downshift to brake unless one is on a very steep hill. Then use the
> engine to brake to keep the brake fluid from boiling (in the extreme), etc.
>
> I'm not sure they're fully up-to-date, for one. Or there's a lot of variation
> from one car make to another re how well clutch parts are designed.

you can get away with all kinds of bad behavior in modern cars. the
reason i gave the cement truck analogy is because heavy equipment like
this is not abuse tolerant. riding the clutch, bad shifting, no engine
braking - all get you stuck at the side of a road with a rapidly
hardening cargo in no time at all. repairing the vehicle is one thing.
crawling inside the hopper with an air hammer to remove all that
concrete is something else.

>
>
>>>And again, correct me if I'm wrong, but apart from downshifting, driving
>
> style
>
>>>will have an impact on clutch life as well. E.g. shifting very quickly.
>>
>>shifting fast has a positive effect on the clutch [if any] but negative
>>on the synchros.
>
>
> I'm not sure we mean the same thing when we say "shift fast."
>
> "Fast shifting will place greater strain on synchronizers as will marginal
> lubrication and the presence of dirt or particulate in the transmission fluid."
> http://www3.bc.sympatico.ca/Volvo_Books/trans1.html

yes, but modern synchros won't let you abuse them, unlike some of the
older designs. you /can't/ shift until it's synched. the old porsche
design [had kind of a baulk ring that ran directly against the dog] was
great if you really needed to shift asap because you could just force
it, but was just not abuse/bad driver tolerant.

>
> But like I said, this is just google stuff that is not all entirely in
> agreement, and I haven't put my hands on the guts of the parts about which we're
> talking. So I'm all eyes if people have more to say on this.
>

hopefully your car maint class will allow you to get your hands on the
workings of a gearbox. alternatively, visit a junk yard some time -
great places to learn.

"jim beam" > wrote
snip
> >>if you want a conclusive demo on the value of synchros/double-clutching,
> >>drive something like a cement truck.
> >
> >
> > My 1.5 liter, under two ton Civic is not a cement truck, so I see your point
but
> > am not sure this would say anything terribly meaningful... Very different
> > engineering and needs being satisfied...
>
> but caroline, you're an engineer. example of extreme is meant to
> illustrate the principle.

I agree it illustrates a principle. But, techies that both you and I are, I
trust you agree that practically speaking not double clutching on a 91 Civic may
have negligible effect on it compared to the life of its other parts.

Not so for the cement truck, it would seem.

> braking in neutral is pretty generally
> inconsequential in a car, but very very dangerous in a truck. the value
> of synchros in a car, especially to a driver that may never have tried
> anything without them, is, imo, not appreciated until a different kind
> of vehicle is experienced. a big truck, where synchros merely assist,
> not override the gear change procedure, is easier/better experience to
> get than finding some old stick-shifting banger with straight cut gears.

Okay. I appreciate the "art of the synchro" here. Seriously!

> > Aside: I'd like to see more reports from others here who have had clutch
parts
> > replaced.
>
> most shops just replace everything - clutch, pressure plate, thrust
> bearing, pilot bearing, and often skim the flywheel too.

Ya but when, and how come someone else with a 91 Civic may have been through a
clutch after only 100k miles?

We've certainly touched on this. Looking for still more empirical data. I did
google the archives a bit and it seems it does happen to Hondas of this vintage.

> personally,
> i'm happy just replacing the clutch plate if everything else is ok. if
> the flywheel is skimmed, the bolt mounting surface needs to be skimmed
> also to maintain the same degree if differential with the friction
> surface that it had when new. frequently, that's not done so people
> wonder why the clutch goes again so soon again after... insufficient
> pressure can be brought by the pressure plate.

I gotta do this sometime... I don't want to hit age 70 without having taken
apart a clutch and having put it back together... :-)

> > I should toss in at this point that Tom 'n' Ray, despite their comments
above,
> > say not to downshift to brake unless one is on a very steep hill. Then use
the
> > engine to brake to keep the brake fluid from boiling (in the extreme), etc.
> >
> > I'm not sure they're fully up-to-date, for one. Or there's a lot of
variation
> > from one car make to another re how well clutch parts are designed.
>
> you can get away with all kinds of bad behavior in modern cars. the
> reason i gave the cement truck analogy is because heavy equipment like
> this is not abuse tolerant. riding the clutch, bad shifting, no engine
> braking - all get you stuck at the side of a road with a rapidly
> hardening cargo in no time at all. repairing the vehicle is one thing.
> crawling inside the hopper with an air hammer to remove all that
> concrete is something else.

Okay.

> > I'm not sure we mean the same thing when we say "shift fast."
> >
> > "Fast shifting will place greater strain on synchronizers as will marginal
> > lubrication and the presence of dirt or particulate in the transmission
fluid."
> > http://www3.bc.sympatico.ca/Volvo_Books/trans1.html
>
> yes, but modern synchros won't let you abuse them, unlike some of the
> older designs. you /can't/ shift until it's synched. the old porsche
> design [had kind of a baulk ring that ran directly against the dog] was
> great if you really needed to shift asap because you could just force
> it, but was just not abuse/bad driver tolerant.

Okay.

> > But like I said, this is just google stuff that is not all entirely in
> > agreement, and I haven't put my hands on the guts of the parts about which
we're
> > talking. So I'm all eyes if people have more to say on this.
> >
>
> hopefully your car maint class will allow you to get your hands on the
> workings of a gearbox.

Yes, I was going to take the manual transmission course but stuff happened.

> alternatively, visit a junk yard some time -
> great places to learn.

Yes, I was thinking of seeing what I could pick up for five bucks at my favorite
import junkyard...

"jim beam" > wrote
snip
> >>if you want a conclusive demo on the value of synchros/double-clutching,
> >>drive something like a cement truck.
> >
> >
> > My 1.5 liter, under two ton Civic is not a cement truck, so I see your point
but
> > am not sure this would say anything terribly meaningful... Very different
> > engineering and needs being satisfied...
>
> but caroline, you're an engineer. example of extreme is meant to
> illustrate the principle.

I agree it illustrates a principle. But, techies that both you and I are, I
trust you agree that practically speaking not double clutching on a 91 Civic may
have negligible effect on it compared to the life of its other parts.

Not so for the cement truck, it would seem.

> braking in neutral is pretty generally
> inconsequential in a car, but very very dangerous in a truck. the value
> of synchros in a car, especially to a driver that may never have tried
> anything without them, is, imo, not appreciated until a different kind
> of vehicle is experienced. a big truck, where synchros merely assist,
> not override the gear change procedure, is easier/better experience to
> get than finding some old stick-shifting banger with straight cut gears.

Okay. I appreciate the "art of the synchro" here. Seriously!

> > Aside: I'd like to see more reports from others here who have had clutch
parts
> > replaced.
>
> most shops just replace everything - clutch, pressure plate, thrust
> bearing, pilot bearing, and often skim the flywheel too.

Ya but when, and how come someone else with a 91 Civic may have been through a
clutch after only 100k miles?

We've certainly touched on this. Looking for still more empirical data. I did
google the archives a bit and it seems it does happen to Hondas of this vintage.

> personally,
> i'm happy just replacing the clutch plate if everything else is ok. if
> the flywheel is skimmed, the bolt mounting surface needs to be skimmed
> also to maintain the same degree if differential with the friction
> surface that it had when new. frequently, that's not done so people
> wonder why the clutch goes again so soon again after... insufficient
> pressure can be brought by the pressure plate.

I gotta do this sometime... I don't want to hit age 70 without having taken
apart a clutch and having put it back together... :-)

> > I should toss in at this point that Tom 'n' Ray, despite their comments
above,
> > say not to downshift to brake unless one is on a very steep hill. Then use
the
> > engine to brake to keep the brake fluid from boiling (in the extreme), etc.
> >
> > I'm not sure they're fully up-to-date, for one. Or there's a lot of
variation
> > from one car make to another re how well clutch parts are designed.
>
> you can get away with all kinds of bad behavior in modern cars. the
> reason i gave the cement truck analogy is because heavy equipment like
> this is not abuse tolerant. riding the clutch, bad shifting, no engine
> braking - all get you stuck at the side of a road with a rapidly
> hardening cargo in no time at all. repairing the vehicle is one thing.
> crawling inside the hopper with an air hammer to remove all that
> concrete is something else.

Okay.

> > I'm not sure we mean the same thing when we say "shift fast."
> >
> > "Fast shifting will place greater strain on synchronizers as will marginal
> > lubrication and the presence of dirt or particulate in the transmission
fluid."
> > http://www3.bc.sympatico.ca/Volvo_Books/trans1.html
>
> yes, but modern synchros won't let you abuse them, unlike some of the
> older designs. you /can't/ shift until it's synched. the old porsche
> design [had kind of a baulk ring that ran directly against the dog] was
> great if you really needed to shift asap because you could just force
> it, but was just not abuse/bad driver tolerant.

Okay.

> > But like I said, this is just google stuff that is not all entirely in
> > agreement, and I haven't put my hands on the guts of the parts about which
we're
> > talking. So I'm all eyes if people have more to say on this.
> >
>
> hopefully your car maint class will allow you to get your hands on the
> workings of a gearbox.

Yes, I was going to take the manual transmission course but stuff happened.

> alternatively, visit a junk yard some time -
> great places to learn.

Yes, I was thinking of seeing what I could pick up for five bucks at my favorite
import junkyard...

Caroline wrote:
> "jim beam" > wrote
> snip
>
>>>>if you want a conclusive demo on the value of synchros/double-clutching,
>>>>drive something like a cement truck.
>>>
>>>
>>>My 1.5 liter, under two ton Civic is not a cement truck, so I see your point
>
> but
>
>>>am not sure this would say anything terribly meaningful... Very different
>>>engineering and needs being satisfied...
>>
>>but caroline, you're an engineer. example of extreme is meant to
>>illustrate the principle.
>
>
> I agree it illustrates a principle. But, techies that both you and I are, I
> trust you agree that practically speaking not double clutching on a 91 Civic may
> have negligible effect on it compared to the life of its other parts.
>
> Not so for the cement truck, it would seem.
>
>
>>braking in neutral is pretty generally
>>inconsequential in a car, but very very dangerous in a truck. the value
>>of synchros in a car, especially to a driver that may never have tried
>>anything without them, is, imo, not appreciated until a different kind
>>of vehicle is experienced. a big truck, where synchros merely assist,
>>not override the gear change procedure, is easier/better experience to
>>get than finding some old stick-shifting banger with straight cut gears.
>
>
> Okay. I appreciate the "art of the synchro" here. Seriously!
>
>
>>>Aside: I'd like to see more reports from others here who have had clutch
>
> parts
>
>>>replaced.
>>
>>most shops just replace everything - clutch, pressure plate, thrust
>>bearing, pilot bearing, and often skim the flywheel too.
>
>
> Ya but when, and how come someone else with a 91 Civic may have been through a
> clutch after only 100k miles?
>
> We've certainly touched on this. Looking for still more empirical data. I did
> google the archives a bit and it seems it does happen to Hondas of this vintage.

the first intent of a clutch is to get used. so what if it wears out?
not using it for its intended purpose it like trying not to use brakes.
or not driving.

clutch life, like with brakes, is a function of the driver. there is
actually a strong argument for slipping the clutch more than might be
assumed from reading so far in this thread. the purpose of the clutch
is to allow both drive-away & smooth shifts. it's entirely feasible to
shift no clutch, but it's hard on the vehicle - motor mounts,
transmission, diff pinions, drive shafts, even the clutch plate torque
springs. harsh shifting causes much greater momentary spike loads in
all these components than does shifting smoothly & using a bit of
clutch. my experience is that stick shift vehicles often wear through
drive shafts much more quickly than than automatics of the same model,
for exactly this reason. there's absolutely no stigma in changing a
clutch at 100k.

>
>
>>personally,
>>i'm happy just replacing the clutch plate if everything else is ok. if
>>the flywheel is skimmed, the bolt mounting surface needs to be skimmed
>>also to maintain the same degree if differential with the friction
>>surface that it had when new. frequently, that's not done so people
>>wonder why the clutch goes again so soon again after... insufficient
>>pressure can be brought by the pressure plate.
>
>
> I gotta do this sometime... I don't want to hit age 70 without having taken
> apart a clutch and having put it back together... :-)

it's just like doing a brake. satisfy your urge at a junk yard.
honestly, it's really nothing interesting unlike cams or injection.

>
>
>>>I should toss in at this point that Tom 'n' Ray, despite their comments
>
> above,
>
>>>say not to downshift to brake unless one is on a very steep hill. Then use
>
> the
>
>>>engine to brake to keep the brake fluid from boiling (in the extreme), etc.
>>>
>>>I'm not sure they're fully up-to-date, for one. Or there's a lot of
>
> variation
>
>>>from one car make to another re how well clutch parts are designed.
>>
>>you can get away with all kinds of bad behavior in modern cars. the
>>reason i gave the cement truck analogy is because heavy equipment like
>>this is not abuse tolerant. riding the clutch, bad shifting, no engine
>>braking - all get you stuck at the side of a road with a rapidly
>>hardening cargo in no time at all. repairing the vehicle is one thing.
>> crawling inside the hopper with an air hammer to remove all that
>>concrete is something else.
>
>
> Okay.
>
>
>>>I'm not sure we mean the same thing when we say "shift fast."
>>>
>>>"Fast shifting will place greater strain on synchronizers as will marginal
>>>lubrication and the presence of dirt or particulate in the transmission
>
> fluid."
>
>>>http://www3.bc.sympatico.ca/Volvo_Books/trans1.html
>>
>>yes, but modern synchros won't let you abuse them, unlike some of the
>>older designs. you /can't/ shift until it's synched. the old porsche
>>design [had kind of a baulk ring that ran directly against the dog] was
>>great if you really needed to shift asap because you could just force
>>it, but was just not abuse/bad driver tolerant.
>
>
> Okay.
>
>
>>>But like I said, this is just google stuff that is not all entirely in
>>>agreement, and I haven't put my hands on the guts of the parts about which
>
> we're
>
>>>talking. So I'm all eyes if people have more to say on this.
>>>
>>
>>hopefully your car maint class will allow you to get your hands on the
>>workings of a gearbox.
>
>
> Yes, I was going to take the manual transmission course but stuff happened.
>
>
>>alternatively, visit a junk yard some time -
>>great places to learn.
>
>
> Yes, I was thinking of seeing what I could pick up for five bucks at my favorite
> import junkyard...
>

you can see /all/ this in a good [bad] junk yard. you don't even have
to buy anything!
http://www.technolab.org/Hako/Katalog-e/Section10.htm

go to a lousy junk yard that has stuff lying about all over the place.
you'll see way more than a place that has everything neatly arranged &
ready for resale.

Caroline wrote:
> "jim beam" > wrote
> snip
>
>>>>if you want a conclusive demo on the value of synchros/double-clutching,
>>>>drive something like a cement truck.
>>>
>>>
>>>My 1.5 liter, under two ton Civic is not a cement truck, so I see your point
>
> but
>
>>>am not sure this would say anything terribly meaningful... Very different
>>>engineering and needs being satisfied...
>>
>>but caroline, you're an engineer. example of extreme is meant to
>>illustrate the principle.
>
>
> I agree it illustrates a principle. But, techies that both you and I are, I
> trust you agree that practically speaking not double clutching on a 91 Civic may
> have negligible effect on it compared to the life of its other parts.
>
> Not so for the cement truck, it would seem.
>
>
>>braking in neutral is pretty generally
>>inconsequential in a car, but very very dangerous in a truck. the value
>>of synchros in a car, especially to a driver that may never have tried
>>anything without them, is, imo, not appreciated until a different kind
>>of vehicle is experienced. a big truck, where synchros merely assist,
>>not override the gear change procedure, is easier/better experience to
>>get than finding some old stick-shifting banger with straight cut gears.
>
>
> Okay. I appreciate the "art of the synchro" here. Seriously!
>
>
>>>Aside: I'd like to see more reports from others here who have had clutch
>
> parts
>
>>>replaced.
>>
>>most shops just replace everything - clutch, pressure plate, thrust
>>bearing, pilot bearing, and often skim the flywheel too.
>
>
> Ya but when, and how come someone else with a 91 Civic may have been through a
> clutch after only 100k miles?
>
> We've certainly touched on this. Looking for still more empirical data. I did
> google the archives a bit and it seems it does happen to Hondas of this vintage.

the first intent of a clutch is to get used. so what if it wears out?
not using it for its intended purpose it like trying not to use brakes.
or not driving.

clutch life, like with brakes, is a function of the driver. there is
actually a strong argument for slipping the clutch more than might be
assumed from reading so far in this thread. the purpose of the clutch
is to allow both drive-away & smooth shifts. it's entirely feasible to
shift no clutch, but it's hard on the vehicle - motor mounts,
transmission, diff pinions, drive shafts, even the clutch plate torque
springs. harsh shifting causes much greater momentary spike loads in
all these components than does shifting smoothly & using a bit of
clutch. my experience is that stick shift vehicles often wear through
drive shafts much more quickly than than automatics of the same model,
for exactly this reason. there's absolutely no stigma in changing a
clutch at 100k.

>
>
>>personally,
>>i'm happy just replacing the clutch plate if everything else is ok. if
>>the flywheel is skimmed, the bolt mounting surface needs to be skimmed
>>also to maintain the same degree if differential with the friction
>>surface that it had when new. frequently, that's not done so people
>>wonder why the clutch goes again so soon again after... insufficient
>>pressure can be brought by the pressure plate.
>
>
> I gotta do this sometime... I don't want to hit age 70 without having taken
> apart a clutch and having put it back together... :-)

it's just like doing a brake. satisfy your urge at a junk yard.
honestly, it's really nothing interesting unlike cams or injection.

>
>
>>>I should toss in at this point that Tom 'n' Ray, despite their comments
>
> above,
>
>>>say not to downshift to brake unless one is on a very steep hill. Then use
>
> the
>
>>>engine to brake to keep the brake fluid from boiling (in the extreme), etc.
>>>
>>>I'm not sure they're fully up-to-date, for one. Or there's a lot of
>
> variation
>
>>>from one car make to another re how well clutch parts are designed.
>>
>>you can get away with all kinds of bad behavior in modern cars. the
>>reason i gave the cement truck analogy is because heavy equipment like
>>this is not abuse tolerant. riding the clutch, bad shifting, no engine
>>braking - all get you stuck at the side of a road with a rapidly
>>hardening cargo in no time at all. repairing the vehicle is one thing.
>> crawling inside the hopper with an air hammer to remove all that
>>concrete is something else.
>
>
> Okay.
>
>
>>>I'm not sure we mean the same thing when we say "shift fast."
>>>
>>>"Fast shifting will place greater strain on synchronizers as will marginal
>>>lubrication and the presence of dirt or particulate in the transmission
>
> fluid."
>
>>>http://www3.bc.sympatico.ca/Volvo_Books/trans1.html
>>
>>yes, but modern synchros won't let you abuse them, unlike some of the
>>older designs. you /can't/ shift until it's synched. the old porsche
>>design [had kind of a baulk ring that ran directly against the dog] was
>>great if you really needed to shift asap because you could just force
>>it, but was just not abuse/bad driver tolerant.
>
>
> Okay.
>
>
>>>But like I said, this is just google stuff that is not all entirely in
>>>agreement, and I haven't put my hands on the guts of the parts about which
>
> we're
>
>>>talking. So I'm all eyes if people have more to say on this.
>>>
>>
>>hopefully your car maint class will allow you to get your hands on the
>>workings of a gearbox.
>
>
> Yes, I was going to take the manual transmission course but stuff happened.
>
>
>>alternatively, visit a junk yard some time -
>>great places to learn.
>
>
> Yes, I was thinking of seeing what I could pick up for five bucks at my favorite
> import junkyard...
>

you can see /all/ this in a good [bad] junk yard. you don't even have
to buy anything!
http://www.technolab.org/Hako/Katalog-e/Section10.htm

go to a lousy junk yard that has stuff lying about all over the place.
you'll see way more than a place that has everything neatly arranged &
ready for resale.

TeGGer® wrote:
>>"jim beam" > wrote
>
>
>>>generally, synchros do last the life of the car.
>
>
>
> They get worn and lose effectiveness, but still work.
>
>
>
>
>>>some of the old
>>>types of synchro, notably some of the early porsche designs, were
>>>great for racing & fast forced shifts, but they wore quickly,
>>>particularly if there were problems with insufficient clutch
>>>disengagement [clutch plate not being sufficiently free to "float" on
>>>the drive pinion], then they'd check out pretty darned quick. the
>>>current cone clutch design of synchro just shrugs off bulk abuse.
>
>
>
>
> Balk rings are just the female half of the synchro assembly. The male half
> bears against this, with the oil film in between.

here's a pic of a porche synchro assembly:
http://www.hako-didactic.de/english/.../HAKO1104g.jpg

from:
http://www.hako-didactic.de/english/...od10/1102.html

ain't no cones in there!

>
> When the revs are mismatched, the balk ring is forced to turn slightly,
> misaligning the pins/teeth/whatever system is used to prevent the synchro
> hub from sliding. Once the two halves have been dragged down to the same
> speed, the rotational force on the balk ring drops to zero, allowing the
> balk mechanism to slide and for hand pressure to push the dog teeth
> together, engaging the synchro hub to the chosen gear.

there's two main types of synchro today; cone type & porsche. both use
something called a baulk ring, but they're utterly different in nature.
in the cone type, it's the part that prevents engagement until
synched. the the porsche, the baulk ring is also the friction surface &
it runs directly against the engagement dog. it won't prevent
engagement if you want to force it because the dog will just press right
over it.

>
> If the synchro friction surfaces wear, it will take longer to drag the two
> halves to the same speed, so you will not be able to rev as high in a gear
> and be able to just move the lever into the next gear as easily as you used
> to.
>
> If you use hypoid or other incorrect lubricant, it will have the same
> effect as if your synchros were worn: It will be difficult or impossible to
> engage a gear unless you double-clutch or shove the lever in really hard.
> That's because the oil film is preventing the synchros from rubbing
> together and matching their speed, so the balk rings will never be allowed
> to move.
>
> Some newer transmissions have double-cone synchros, which doubles the
> sliding surface area, giving smoother shifts as well as longer life.

TeGGer® wrote:
>>"jim beam" > wrote
>
>
>>>generally, synchros do last the life of the car.
>
>
>
> They get worn and lose effectiveness, but still work.
>
>
>
>
>>>some of the old
>>>types of synchro, notably some of the early porsche designs, were
>>>great for racing & fast forced shifts, but they wore quickly,
>>>particularly if there were problems with insufficient clutch
>>>disengagement [clutch plate not being sufficiently free to "float" on
>>>the drive pinion], then they'd check out pretty darned quick. the
>>>current cone clutch design of synchro just shrugs off bulk abuse.
>
>
>
>
> Balk rings are just the female half of the synchro assembly. The male half
> bears against this, with the oil film in between.

here's a pic of a porche synchro assembly:
http://www.hako-didactic.de/english/.../HAKO1104g.jpg

from:
http://www.hako-didactic.de/english/...od10/1102.html

ain't no cones in there!

>
> When the revs are mismatched, the balk ring is forced to turn slightly,
> misaligning the pins/teeth/whatever system is used to prevent the synchro
> hub from sliding. Once the two halves have been dragged down to the same
> speed, the rotational force on the balk ring drops to zero, allowing the
> balk mechanism to slide and for hand pressure to push the dog teeth
> together, engaging the synchro hub to the chosen gear.

there's two main types of synchro today; cone type & porsche. both use
something called a baulk ring, but they're utterly different in nature.
in the cone type, it's the part that prevents engagement until
synched. the the porsche, the baulk ring is also the friction surface &
it runs directly against the engagement dog. it won't prevent
engagement if you want to force it because the dog will just press right
over it.

>
> If the synchro friction surfaces wear, it will take longer to drag the two
> halves to the same speed, so you will not be able to rev as high in a gear
> and be able to just move the lever into the next gear as easily as you used
> to.
>
> If you use hypoid or other incorrect lubricant, it will have the same
> effect as if your synchros were worn: It will be difficult or impossible to
> engage a gear unless you double-clutch or shove the lever in really hard.
> That's because the oil film is preventing the synchros from rubbing
> together and matching their speed, so the balk rings will never be allowed
> to move.
>
> Some newer transmissions have double-cone synchros, which doubles the
> sliding surface area, giving smoother shifts as well as longer life.

TeGGer® wrote:
> jim beam > floridly penned in
> :
>
> <snip>
>
>
>>there's two main types of synchro today; cone type & porsche. both
>>use something called a baulk ring, but they're utterly different in
>>nature.
>> in the cone type, it's the part that prevents engagement until
>>synched. the the porsche, the baulk ring is also the friction surface
>>& it runs directly against the engagement dog. it won't prevent
>>engagement if you want to force it because the dog will just press
>>right over it.
>
>
>
>
> I wish I had a bigger picture; I'd love to study the construction more
> closely. Looks a bit different from Toyota T-40 4-speed I pulled apart.
>
> Either way, it's conceptually the same as any other synchro design: You
> have two friction surfaces which are separated by a thin skin of oil that
> is easily sheared under stress. When those friction surfaces wear, the
> synchros cannot synchronize as quickly, and you will have difficulty
> changing gear unless you double-clutch.

true. they're both very interesting though. fwiu the cone type clutch
is fundamentally less prone to wear. the majority of the cone surfaces
are covered in oil & metal to metal sliding contact is minimal as i'm
told that there is a reasonable degree of friction within the oil shear
layer as they get close. the porsche type relies on direct metal to
contact - and has a rough sand-cast exterior for just this purpose. the
baulk ring locks by self-activating expansion against the inside of the
dog, much like a band clutch locks a ratio in a planetary automatic gearbox.

to be honest, i've not played with the cone type synchros as much as the
porsche type - basically because i've not had as many vehicles with that
type synchro fail like i have had the porsche type. as you say, second
gear [on that type of box] goes all the time.

>
> Double-clutching saves the synchros from some of their work.
>

indeed. it's the /only/ way to drive a car with a dud synchro!

TeGGer® wrote:
> jim beam > floridly penned in
> :
>
> <snip>
>
>
>>there's two main types of synchro today; cone type & porsche. both
>>use something called a baulk ring, but they're utterly different in
>>nature.
>> in the cone type, it's the part that prevents engagement until
>>synched. the the porsche, the baulk ring is also the friction surface
>>& it runs directly against the engagement dog. it won't prevent
>>engagement if you want to force it because the dog will just press
>>right over it.
>
>
>
>
> I wish I had a bigger picture; I'd love to study the construction more
> closely. Looks a bit different from Toyota T-40 4-speed I pulled apart.
>
> Either way, it's conceptually the same as any other synchro design: You
> have two friction surfaces which are separated by a thin skin of oil that
> is easily sheared under stress. When those friction surfaces wear, the
> synchros cannot synchronize as quickly, and you will have difficulty
> changing gear unless you double-clutch.

true. they're both very interesting though. fwiu the cone type clutch
is fundamentally less prone to wear. the majority of the cone surfaces
are covered in oil & metal to metal sliding contact is minimal as i'm
told that there is a reasonable degree of friction within the oil shear
layer as they get close. the porsche type relies on direct metal to
contact - and has a rough sand-cast exterior for just this purpose. the
baulk ring locks by self-activating expansion against the inside of the
dog, much like a band clutch locks a ratio in a planetary automatic gearbox.

to be honest, i've not played with the cone type synchros as much as the
porsche type - basically because i've not had as many vehicles with that
type synchro fail like i have had the porsche type. as you say, second
gear [on that type of box] goes all the time.

>
> Double-clutching saves the synchros from some of their work.
>

indeed. it's the /only/ way to drive a car with a dud synchro!

TeGGer® wrote:
> jim beam > floridly penned in
> :
>
>
>>TeGGer® wrote:
>
>
>>to be honest, i've not played with the cone type synchros as much as
>>the porsche type - basically because i've not had as many vehicles
>>with that type synchro fail like i have had the porsche type. as you
>>say, second gear [on that type of box] goes all the time.
>
>
>
> You'd be surprised how tiny some of those "cones" really are, like a ring
> 1/4" wide.

yes, i've taken them apart before - just not had the opportunity of
testing the results of my having messed with them!

>
>>>Double-clutching saves the synchros from some of their work.
>>>
>>
>>indeed. it's the /only/ way to drive a car with a dud synchro!
>
> Yep. The Integra's second synchro is on its way out right now. I can't rev
> any higher than 4K RPM anymore unless I want to let the revs drop to 3,000
> before the lever will move. Shifting at 3,500 seems to be about right for
> second now.
>
> The second gear hub on this car *also* carries the reverse gear hub. The
> extra mass of that combined with the 1,500 RPM spread between 1st and 2nd
> is, I'm sure, the reason second is relatively weak in these cars.

that's possible, but second is always the first to go on any car,
regardless of make. 1-2 has the biggest ratio difference and is much
more frequently rushed. it also gets the effects of the first shift on
the coldest oil!