Honda Car Forum

> "jim beam" <nospam@example.net> 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.

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.

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®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

jim beam <nospam@example.net> floridly penned in
news:yY6dnVF5re_i7TbcRVn-vA@comcast.com:

> Caroline wrote:

>> 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.
>


Matching your revs then releasing the clutch as quickly and smoothly as
possible will be benficial to clutch life, since you minimize sliding.

Shoving the shift lever from slot to slot quickly will accelerate wear on
shift forks, dog teeth, synchros, all kinds of parts.

--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

Caroline wrote:
> "jim beam" <nospam@example.net> 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" <nospam@example.net> 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.

jim beam <nospam@example.net> floridly penned in
news:9OSdnbzTAJLHPjbcRVn-hQ@comcast.com:

<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.

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


--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

TeGGer® wrote:
> jim beam <nospam@example.net> floridly penned in
> news:9OSdnbzTAJLHPjbcRVn-hQ@comcast.com:
>
> <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!

jim beam <nospam@example.net> floridly penned in
news:nM6dnfx8dYd0eTbcRVn-hQ@comcast.com:

> 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.

>
>>
>> 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.


--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

TeGGer® wrote:
> jim beam <nospam@example.net> floridly penned in
> news:nM6dnfx8dYd0eTbcRVn-hQ@comcast.com:
>
>
>>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!

jim beam wrote:
<...>
> you don't "need" to go 5-4-3-2-1 by the way. 5-3-1 is perfectly ok.
> 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. 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.

AND if the engine just happens to cough and die, there you are
with no vacuum for the breaks and no power for the steering
either!


--
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Dorset UK Astro Society's Web pages, Info, Meeting Dates, Sites & Maps
Change 'news' to 'sewn' in my Reply address to avoid my spam filter.

TeGGer® wrote:
> Copper grease or M77 , not silicone, goes there. Check my Brake Service
> pages again for photos of where to put the grease.

Couldn't find copper grease. I wound up just using a dab of the CRC
brake caliper grease on the edges of the pad backing plate, where it
sits in the stainless mounting clips, and around the edge of the piston
where it hits the shim.

> Rubber should be fine. It lasts a long time. If it is aged and brittle,
> you'll know the instant you try to pull it out of the groove.

The rubber is indeed fine. Aging, yes, but still supple enough that I
was able to pull it back and apply a bit of brake fluid in the pinch--I
couldn't find silicone grease by the time I had to do the job, ad it
appears that my pistons are starting to rust in the boot groove. I
scraped out a bit of it, but I'll either have to pull the pistons out,
sand, and replace, applying silicone grease then, or replace the
calipers when they seize. I did not see rust further in than the groove,
but that's of course only a matter of time unless I stop it.

At the moment I can't decide which would be easier--probably just doing
the piston, unless the bore is rusted, too, so maybe wholesale
replacement is in order. Probably no way to know how long I can wait,
but perhaps it will be a project for next summer. Suppose I could check
the fluid in the spring to see how dirty it is, and just change it more
frequently if necessary, for a while.

> It's hard to turn because it's so big and may be gummed up, but you CAN
> turn it. Put silicone in first, work the piston in and out a few times to
> loosen it up, then try to turn it. You need to eject it enough to pull the
> dust boot off the groove in the piston. Make sure you don't scar up the
> piston inboard of the boot groove.

In fact I was able to turn it by grabbing the edge firmly with a pliers
and turning it. Did take a good deal of effort, but I was able to turn
it about halfway around to get at the groove rust I mentioned.

The upshot is... the piston wasn't stuck, and the pins are fine (I did
apply more grease while there). Must have been rust sticking the pad
edges in place--it was pretty firmly stuck there, I did have to use a
screwdriver to pry it out. The rear pins are starting to bind a tad on
the left (only one I had time to check), and since the pins are fine I
assume it has to be the bore. See below.

I took a bunch of rust out, but foolishly didn't think to apply grease
between the stainless clips and the caliper tabs they abut--i.e., on the
other side of the stainless lip from the pad backing plate edge. Ahh
well. I'll keep an eye on it. I do need a better way to sand down those
tabs. Perhaps a wire brush drill attachment next time.

Anyhow, got the pads replaced and the fluid changed. Boy, was it a nice
coffee color--after pushing the problem caliper piston in with the
clamp, the reservoir was swirling with rust, and the other lines were
similar. Lord knows the last time it was changed, and I have to assume
there's rust in the bore that will be a problem at some point.

I also checked the left rear caliper, where the p-brake isn't working.
Tried screwing the piston all the way in, and was also able to screw it
out (not all the way, of coures). Applying the main brake pushed the
piston out, and releasing the main brake allowed it to retract.

Applying the p-brake did nothing, however--no piston movement, whether
the piston was completely screwed in, or screwed out somewhat. I did not
have time at that point to compare the action on the right side, but I
presume it's supposed to push the piston out.

What bothers me about this failure is that the rear calipers were
supposedly replaced at 111,494. The local dealer noted that the p-brake
"needed attention" when I had the car inspected prior to purchase at
113K, and there's no way a caliper should fail within 1600 miles. Damn.
Why the bore would be rusted so fast, too, I dunno. I've contacted the
previous owner to see if it's possible to pursue it, but it may not be,
or be worth it--especially since she threw out the receipts when I
bought it!! More and more I'm finding out why that was a terrible
thing... hope there's no more. Sheesh.

Many thanks for everyone's help here, especially you, Tegger. I've now
done my first brake job, and am invincible!! <vbg> (actually wasn't hard
at all; now, a timing belt I might leave to a shop)