Edit: 2021-06-01 - 19:08 EST
I originally created and posted this thread: 2007-03-08 - 16:35 EST and hosted the pictures with photobucket. I am now re-uploading the pics to Honda-Tech directly. I am currently discussing with a customer the 2nd gear issues that he is having with his FK8 Civic Type R transmission, and despite the fact that I originally created this post about D-series transmissions, the information is still applicable. FK8 Civic Type R uses triple cone synchros for 1st and 2nd, dual cone for 3rd and 4th, and single cone for 5th and 6th. There are no synchro cones on FK8 1st - 4th gears, as the synchro cones are part of the triple or dual cone synchros respectively. However, each of those gears still have similar synchro teeth, and synchro sleeves that wear in the same manner. -- I am also going to leave my original dialogue in here exactly how it was when I originally posted this in 2007.
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

I've explained this several times over an IM conversation and I'm just getting sick of doing it. So I'll continue to clean this up to try to make it easier on myself to explain to you guys

I'll do my best to explain using a D16Y8 2nd gear as example.

Here is a picture of an assembled d16y8 countershaft (thanks Jason!)




I'm going to try to keep from getting too technical here, so someone might read this and be like (you left a bunch of stuff out. Yes, Mista Bone I mean you )

okay, here we go:

The following items are locked onto the countershaft and they don't spin:
synchro hub
synchro sleeve
the synchro sleeve can freely move a slight amount (see the brass tab that is between the synchro hub teeth)

2nd gear spins at high rpms on the countershaft.

When you are engaging 2nd gear the synchro sleeve slides down towards 2nd gear. When this occurs the brass synchro bites down onto the gear cone (pictures below) and it acts like a brake that stops 2nd gear from spinning. That's it. All it is is a brake pad for your gears!

After many many gear shifts, the synchro teeth begin to wear out. Just like a brake pad would. Eventually they will wear out so much that it will be the dog teeth hitting the teeth on the synchro sleeve. This is what happens when gears "GRIND"

So what happens when the gears grind long enough? The dog teeth start to wear out and the sleeve is no longer able to fully engage the gear. When this happens, your gears begin popping out of gear.

synchro sleeve (note the dog teeth on the inside)



New synchro, notice the ribbed teeth that bite down onto the gear cone.




you can see the gear cone here, also notice how worn out the dog teeth are.




A way of measuring the life of the synchros (92-95 D trans)


Ignore these pics for now, I'll elaborate on gear cone scuffing later
http://i107.photobucket.com/al...5.jpg

http://i107.photobucket.com/al...7.jpg

 

will do.

 

Thank you so much tranny guru.

i want a step by step picture tutorial on rebuilding/changing syncros on a tranny

 

http://www.xm-parts.com/articles/hgear/gear.htm

rebuild tranny

 

good write up

 

thank you! at least now i understand why my car grinds going into second when i try to shift fast. Would having a short throw shifter have any effect on wear and grinding? I as many have heard alot of different things.

 

only if you are shifting too fast for the synchro to slow down or speed up (match gear speed) of the gear.

 

pm'd you a question, sorry for the newbieness.

 

any reason why my sleeve would be bad and not so much the syncro?

 

Bense, unrelated question: is the indentation pattern on that helical gear normal or a sign of wear on just that set?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clayne &raquo;</TD></TR><TR><TD CLASS="quote">Bense, unrelated question: is the indentation pattern on that helical gear normal or a sign of wear on just that set?</TD></TR></TABLE>

New gear from the dealership in the bag has those indentations.

I love waiting 4 months to respond to questions

 

I've got a K20A2 (X2M5) second gear that has been pounded into failure and maybe a synchro hub that has signs of chatter on it if you want pictures to show people what to look for in terms of failure modes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clayne &raquo;</TD></TR><TR><TD CLASS="quote">Bense, unrelated question: is the indentation pattern on that helical gear normal or a sign of wear on just that set?</TD></TR></TABLE>

those notches are for oiling purposes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mista Bone &raquo;</TD></TR><TR><TD CLASS="quote">

those notches are for oiling purposes.

</TD></TR></TABLE>

We use them for Identification purposes

 

good write up!

 

all of my dog teeth seem to have some wear on them (a little bit rounded).
I will be replacing the synchros... but how big of a deal are the dog teeth??
should i replace them, or are they not that big of a deal?

they arent quite as bad as the last pic that Bense posted earlier...

thanks




Modified by cachehx at 8:38 PM 12/25/2007

 

Great writeup. Now I know why my car is popping out of 5th.

 

don't forget to debur the backsides

 

don't forget to what?


i've been away from H-T for a while. all the ads suck.

 

about to go fix my tranny right now!! lol

 

The picture posted by Bense is pretty extreme (not uncommon, but extreme). The only way to know for sure if yours are bad or acceptable is to see them. Dog teeth are extremely important, but don't have to be flawless to be run-able (did i just make a word up? ). Hope this is helpful

 

Anyone have an idea around how many miss shift/grinds until your gear grinds every time ? Just wondering

 

42

 

up