Downshift from 2nd to 1st (GRINDING!)
S. Daigle
I bought a 2000 Honda Accord EX/Leather (4cyl. 5spd.) last year... I now
have 19000kms (12000 miles) on it. Last weekend, it suddenly started to
grind like hell while I downshifted from 2nd to 1st while driving at only
10kms/hr (6 miles/hr). I've owned the car for the past 7 months, and never
had that problem before. Just before that happened, I could easily
downshift from 2nd to 1st at any speed under 50kms/hr (31 miles/hr) without
a single grind. (I know that there's no reason why I should downshift form
2 to 1 at 50kms/hr... but just to tell you that I could). Anyway, I took
the car in at the Honda dealer today and asked them about this problem.
They told me that the transmission works like new... it's supposed to grind
when downshifting to 1st gear if the car isn't stopped. Then I asked the
technician to try out a new Accord and see what happens. So he did... he
downshifted from 2nd to 1st with the other Accord at speeds well over 40
km/s per hour without a problem (no grinding). Right now, there's no way
that I can downshift to 1st unless driving under 5 kms/hr... at about 10
kms/hr, it grinds like crazy.
I know that normaly, the 1st gear isn't synchronized and you can't
downshift into it at hign speeds... but in my manual, it says "All forward
gears are synchronized to insure smooth shifting". Does this mean that my
first gear is syncronized??? Why can't I downshift into 1st while my
vehicle is moving...??
Any suggestions? Thanks,
Shaun.
TeGGeR
for the last thirty-five years or more.
You've just taken the edge off your synchros is what you've done. Go read up
on double-clutch downshifting. This is an advanced technique which you can
downshift into first on the move without damaging your synchros.
First gear is geared very tall, in order to maximize torque available at the
wheels so as to let you get the car moving more easily. Unfortunately, this
also means that the rotational difference between first and the other gears
is very great, and if you drag right down from second to first, the synchros
have to work like crazy to drag the balk rings and dog clutches into some
semblance of similar rpms before shifting is permitted. When the synchros
start to wear, the dog clutches will begin to scuff together at high
rotational difference, resulting in the grinding you hear.
Three tips to help you prevent further damage to your transmission:
1) Stop shifting into first with the car moving, at least until you
understand exactly what you're doing, and have mastered double-clutch
downshifting.
2) When coasting up to a red light, don't row down through the gears, just
put it in neutral, let go of the clutch, and use the brakes only.
3) Make sure your clutch is properly adjusted, and don't ride the pedal.
--TeGGeR
"S. Daigle" <gn...@hotmail.com> wrote in message
news:NbDm6.1627$br1....@sodalite.nbnet.nb.ca...
NB13
97hb
TeGGeR
feet to get going.
--TeGGeR
"NB13" <hai...@haint13.net> wrote in message
news:3A9B0B5F...@haint13.net...
> I hate transmissions.
>
> 97hb
ralph
more.
--
The first rule of fart club is:
you don't talk about fart club.
Kevin McMurtrie
can fix it.
The grinding doesn't hurt anything. I ground 2nd and 3rd gear like hell
for months on an 88 Tercel. When I got the faulty parts back (dirt
packed in oil escape grooves) there was absolutely no visible damage.
The gears are made of a tough steel alloy similar to gun metal.
(but the sound does suck)
In article <NbDm6.1627$br1....@sodalite.nbnet.nb.ca>, "S. Daigle"
Gerald Wang
Pars <pars_r...@trebnet.com> wrote:
>Downshifting into first should be left to those sport cars that have double
>syncros for the first gears.
Could you explain to me what "double synchros" are?
Thanks,
Gerald
S. Daigle
has them. Here's an extract from this website: http://www.nsxprime.com/
"The first gear synchro in the NSX is unusual in that it has two cones,
effectively two synchros, to help it engage. This makes it slightly more
difficult to move the lever, but insures a matched speed on engagement."
I hope this helps answer your question.
Shaun
Gerald Wang <gtw...@calum.csclub.uwaterloo.ca> wrote in message
news:97h8rj$l90$2...@watserv3.uwaterloo.ca...
S. Daigle
thanks for the numerous replies. The honda dealer ordered new synchros
for all my gears (altough he's still arguing that there's no synchro on
first gear) and he'll place them all for free. One more question... is it
possible that a synchro from another gear (ex: 3rd gear) is the synchro
responsible for synchronizing the first gear? The honda technician told me
that the 5th gear synchro is partly responsible to synchronize my reverse
gear.
The only 2 replies containing possible causes were that it's possible
that I clipped the edge of my synchro and the other says that it could be a
loose clip. I didn't understand the first one. Are they other possible
causes for this problem?
As for the double clutching idea, it's something that I rearely
preformed, but if it's that much of a help for my synchros, I'll definitelly
use it more often.
Any more insight on the subject is greatly appreciated. Again, thanks
for your help.
Shaun
S. Daigle <gn...@hotmail.com> wrote in message
news:NbDm6.1627$br1....@sodalite.nbnet.nb.ca...
Kevin McMurtrie
<gn...@hotmail.com> wrote:
>Hi,
>
> thanks for the numerous replies. The honda dealer ordered new
> synchros
>for all my gears (altough he's still arguing that there's no synchro on
>first gear) and he'll place them all for free. One more question... is it
>possible that a synchro from another gear (ex: 3rd gear) is the synchro
>responsible for synchronizing the first gear? The honda technician told
>me
>that the 5th gear synchro is partly responsible to synchronize my reverse
>gear.
Hold on! The dealer says there's no 1st gear synchro and you're still
having that place do the work?!?!?!?!?
There absolutely IS a first gear synchro. There isn't a reverse synchro
but Honda does seem to have a trick for bumping reverse into alignment
when you're at a complete stop.
Cancel your repair and take the work somewhere else. Don't let them
touch the car! You don't need all synchros changed. At most you need a
new synchro for first gear. (I suspect a clip because you said the
problem was sudden)
TeGGeR
"Kevin McMurtrie" <mcmu...@sonic.net> wrote in message
news:mcmurtri-057E15...@news.sonic.net...
> In article <NOWm6.1823$br1....@sodalite.nbnet.nb.ca>, "S. Daigle"
> <gn...@hotmail.com> wrote:
>
> >Hi,
> >
> > thanks for the numerous replies. The honda dealer ordered new
> > synchros
> >for all my gears (altough he's still arguing that there's no synchro on
> >first gear) and he'll place them all for free. One more question... is
it
> >possible that a synchro from another gear (ex: 3rd gear) is the synchro
> >responsible for synchronizing the first gear? The honda technician told
> >me
> >that the 5th gear synchro is partly responsible to synchronize my reverse
> >gear.
First/second and third/fourth share the same synchro, balk ring and dog
clutch *assembly*, with the shift fork in the middle, but the friction
surfaces and dog teeth themselves are unique to each gear. Fifth and reverse
share some parts too, but only fifth has a synchro. I suspect the dealer's
not making himself clear on what exactly has a synchro and what doesn't.
I'm not sure why (other than marketing) anybody puts a synchro on first, as
the rotartional difference is usually so great that it takes a mighty shove
to overcome the balk rings and force the shift lever into first against its
will.
>
> Hold on! The dealer says there's no 1st gear synchro and you're still
> having that place do the work?!?!?!?!?
>
> There absolutely IS a first gear synchro. There isn't a reverse synchro
> but Honda does seem to have a trick for bumping reverse into alignment
> when you're at a complete stop.
That's the bevel on the reverse gear teeth. Reverse is the only gear that
actually slides on the shaft, rather than being in constant mesh with the
countershaft gear and relying on dog clutch engagement to lock it to the
shaft.
>
> Cancel your repair and take the work somewhere else. Don't let them
> touch the car! You don't need all synchros changed. At most you need a
> new synchro for first gear. (I suspect a clip because you said the
> problem was sudden)
>
>
>
> > The only 2 replies containing possible causes were that it's possible
> >that I clipped the edge of my synchro and the other says that it could be
> >a
> >loose clip. I didn't understand the first one. Are they other possible
> >causes for this problem?
That was me, TeGGeR. I was using a figure of speech when I said "took the
edge off your synchro".
What you did in fact was to wear off some of the friction surface of the
synchro faster than normal. Taking the "edge" off meant damaging it through
excessive friction, not actually breaking a sharp edge off of anything. Poor
choice of words on my part.
The balk rings will prevent engagement until both halves of the synchro are
more or less rotating the same, and only then will allow the dog clutches to
engage, allowing the shift lever to move into gear. Worn synchros will
result in the synchros having a harder time making the revs match, and the
balk rings will wear too, so the dog clutches will be allowed to try to
engage when they are not stationary relative to each other, and you will get
the grinding noise.
--TeGGeR
Gerald Wang
S. Daigle <gn...@hotmail.com> wrote:
>"The first gear synchro in the NSX is unusual in that it has two cones,
>effectively two synchros, to help it engage. This makes it slightly more
>difficult to move the lever, but insures a matched speed on engagement."
>
>I hope this helps answer your question.
Yes, it does. Thank you Shaun!
Gerald
CaptainKrunch
Considering your shifting into first gear when you should be in second.
First gear is for starting off and not slowing down. I suppose you will
learn the hard way. I suggest you learn how to drive and be damn thankful
your car is being fixed for free.
In support of you however....the vehicle most certainly will have a first
gear synchro, this synchro is the first/second gear synchro. Perhaps the
Honda guy should look at the Factory service manual section 13. There is
a third/fourth gear synchro and a separate fifth gear synchro. Reverse
is simply a sliding, unsynchronized, straight cut gear. That is why
reverse gear whines like it does. The teeth are straight cut not helical
cut like all of the other gears. In addition the reverse gear is at the
other end of the mainshaft/countershaft and not in any way connected to the
fifth gear, and/or fifth gear synchro.
To avoid any further problems you may want to purchase the factory
electrical manual and the factory service manual from www.helminc.com.
They will pay for themselves with one repair most likely. This way you
will have the information in front of you and you wont have to depend on
any other morons for an answer to any of your questions.
"S. Daigle" <gn...@hotmail.com> wrote in message
news:NOWm6.1823$br1....@sodalite.nbnet.nb.ca...
ralph
always the 1-2 that needs replacing, so all the rest are just $$$$.
--
HogDoctor
> Hi,
>
> thanks for the numerous replies. The honda dealer ordered new synchros
> for all my gears (altough he's still arguing that there's no synchro on
> first gear) and he'll place them all for free.
>
> Any more insight on the subject is greatly appreciated. Again, thanks
> for your help.
>
>
I was driving my civic (5 speed) around today and actually paid attention to my
shifting, I noticed
that I only downshift to 2nd, and unless I'm almost stopped completely, I won't
bother
going to 1st, and when I tried while moving, it really didn't want to go, so I
didn't push it.
Shifting into 1st at 30 mph may have been challenging the synchro beyond it's
capabilities,
and it finally gave up.
--
HogDr SENS BS#123
---------------------------------------------------------------
HD Dealer Technician at your service......
My Employer's site: http://www.wishd.com
My site: http://www.execpc.com/~patrickz/patricksite.htm
---------------------------------------------------------------
George Macdonald
>Hi,
>
> thanks for the numerous replies. The honda dealer ordered new synchros
>for all my gears (altough he's still arguing that there's no synchro on
>first gear) and he'll place them all for free. One more question... is it
>possible that a synchro from another gear (ex: 3rd gear) is the synchro
>responsible for synchronizing the first gear? The honda technician told me
>that the 5th gear synchro is partly responsible to synchronize my reverse
>gear.
This dealer/tech is very confused: no synchro on first gear but the reverse
one does?? They have also seem to have ordered parts which they claim do
not exist.:-)
Hondas do not have a synchromesh reverse - some Toyotas do though - other
than using the first gear synchro sleeve in conjunction with the straight
cut reverse idler gear. The 1st & 2nd gears use a common synchro hub and
sleeve on the counter shaft; the 3rd & 4th gears use a common synchro
hub/sleeve on the mainshaft and of course each individual gear has its own
synchro ring. It makes sense if you think about your gear lever pattern:
push the gear lever forward into first and the shift fork slides the sleeve
along the hub engaging first; pull it back and the same sleeve slides in
the opposite direction engaging 2nd gear.
5th gear has a separate synchro sleeve/ring assembly on the mainshaft but
again, if you think about it, its shift fork is part of the same assembly
as the reverse fork. That's the only association between the two.
> The only 2 replies containing possible causes were that it's possible
>that I clipped the edge of my synchro and the other says that it could be a
>loose clip. I didn't understand the first one. Are they other possible
>causes for this problem?
A common cause of grinding like you report is a cracked synchro ring - it
still works, just not as well when the ring gets loaded and distorts due to
the crack. There could also be some tooth edge damage. There are also
some extra bits in the 1st/2nd synchro mechanism due to the higher speeds
they work at - double cone synchro ring for 2nd and friction dampers for
1st and 2nd - and it's possible there's some breakage or premature wear
there.
> As for the double clutching idea, it's something that I rearely
>preformed, but if it's that much of a help for my synchros, I'll definitelly
>use it more often.
>
> Any more insight on the subject is greatly appreciated. Again, thanks
>for your help.
Like others have said, if you think of the relative speeds of the various
parts and the rpms of your engine in 1st gear at that road speed under
acceleration, look at it from the opposite direction: by shifting into
first at that speed you're using the synchro ring and cone mechanism to
force the mainshaft to spin up to that same rpms. I think most people
agree it's abusing the gear box and it'll wear out quicker. As far as I
can tell, 1st gear does not have a double cone synchro ring like 2nd so
it's really not made for the job.
I'm not sure why you want to shift down into 1st at these speeds anyway
(are you auto-crossing or racing ?) but if you consider it an advantage
learn to double clutch well. You'll still be beating the hell out of all
the bearings in the gearbox though.
Rgds, George Macdonald
"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??
George Macdonald
wrote:
I took a look at a couple of service manuals and the current Accord has a
double synchro ring for 2nd gear but not for 1st; same with the '92 Integra
GS-R, but not the regular Integra of same years. It basically consists of
a 3 piece synchro ring assembly - an outer ring with the dog teeth and
inner ring with grooves, separated by a cone. Evidently the 2nd gear is
made to take more "abuse" than 1st.
S. Daigle
again, thanks for the replies. It may seem that I'm trying to downshift
to 1st gear at great speeds, but I'm not. I was simply trying to make a
point to the technician that it's normally possible, even without double
clutching. I was then trying to prove to him that it was also IMPOSSIBLE to
downshift to 1st gear below 10 kms/hr (6 miles/hr) without grinding the
gears. The only time that I downshift to 1st, is below 15kms/hr (9.3
miles/hr) and even then, I almost always double clutch.
Anyway, from the numerous replies I received, it seems that I'll have to
teach Honda's Transmission Techincian a thing or two.
Thanks a million,
Shaun
S. Daigle <gn...@hotmail.com> wrote in message
news:NbDm6.1627$br1....@sodalite.nbnet.nb.ca...
Gerald Wang
George Macdonald <fammacd=!SPAM^noth...@garden.net> wrote:
>I took a look at a couple of service manuals and the current Accord has a
>double synchro ring for 2nd gear but not for 1st; same with the '92 Integra
>GS-R, but not the regular Integra of same years. It basically consists of
>a 3 piece synchro ring assembly - an outer ring with the dog teeth and
>inner ring with grooves, separated by a cone. Evidently the 2nd gear is
>made to take more "abuse" than 1st.
Thanks for looking into this, George. It's interesting that they use it
on the Accord as well.
Regards,
Gerald
Pars
George Macdonald wrote:
> On 27 Feb 2001 22:14:11 GMT, gtw...@calum.csclub.uwaterloo.ca (Gerald Wang)
> wrote:
>
> >In article <3A9BECC9...@trebnet.com>,
> >Pars <pars_r...@trebnet.com> wrote:
> >>Downshifting into first should be left to those sport cars that have double
> >>syncros for the first gears.
> >
> >Could you explain to me what "double synchros" are?
>
> I took a look at a couple of service manuals and the current Accord has a
> double synchro ring for 2nd gear but not for 1st; same with the '92 Integra
> GS-R, but not the regular Integra of same years. It basically consists of
> a 3 piece synchro ring assembly - an outer ring with the dog teeth and
> inner ring with grooves, separated by a cone. Evidently the 2nd gear is
> made to take more "abuse" than 1st.
Interesting fact about the Accord having double syncro in 2nd gear. I was
first introduced by the double-syncro term from my friends MR2. Apparently
that car has it on 1st, 2nd and 3rd gear. It was kinda interesting after 95,000km
of abuse (just before the warranty expired) the syncros on the 4th gear died on
him.
Gerald Wang
found another interesting tidbit:
Ford's MTX-75 gearbox (used in the Contour/Mystique/New Cougar/Zetec
Focus) has double synchronization on 1st, 2nd, and 3rd gear. In
addition, the reverse gear is synchronized as well.
Gerald
S. Daigle
Shaun
Gerald Wang <gtw...@calum.csclub.uwaterloo.ca> wrote in message
news:97m3fn$nh7$1...@watserv3.uwaterloo.ca...
Doug
covered under warranty. Also, both our honda and acura don't like shifting
into first if they're still moving.news:NOWm6.1823$br1....@sodalite.nbnet.nb.ca...
DRGNRX-7
Doug <doug....@home.com> wrote in message
news:wjDr6.32050$p66.10...@news3.rdc1.on.home.com...
> I wouldn't shift into first to slow down -next time it breaks it may not
be
> covered under warranty. Also, both our honda and acura don't like
shifting
> into first if they're still moving.
That is weird, and it sort of sucks if you are into performance racing. I
can shift into first doing 15 mpg easily. No damage here. Although RX-7's
are different.
DRGNRX-7
DRGNRX-7 <87...@rx-7.net> wrote in message
news:fxDr6.322053$j6.45...@news1.rdc1.va.home.com...
>
> Doug <doug....@home.com> wrote in message
> news:wjDr6.32050$p66.10...@news3.rdc1.on.home.com...
> > I wouldn't shift into first to slow down -next time it breaks it may not
> be
> > covered under warranty. Also, both our honda and acura don't like
> shifting
> > into first if they're still moving.
>
> That is weird, and it sort of sucks if you are into performance racing. I
> can shift into first doing 15 mpg easily. No damage here. Although RX-7's
> are different.
err, that is 15 mph.