Johnny_9

How crucial is this for shift quality?

Is the clutch handing off the mainshaft?

Aquafina

iTrader: (3)

Pretty crucial.

Very crucial for longevity of the trans. Also affects power loss through the trans.

The clutch mounts on the mainshaft. The mainshaft mounts on two bearings in the trans and one in the flywheel.

Johnny_9

...I have not seen my mechanic do it :-) how about in your experience?

Also the stockist doesnt keep a full set of clearance shims in ready stock...

Aquafina

iTrader: (3)

I don't understand what you mean in my experience? I set the mainshaft and diff shim clearance on every trans I build.

As far as shims in stock, you'll just need to see which one you need and order it. Order all of them if you're not sure and are on a time limit.

TwotoneC1Da9

im having the same problem i bought a itr case with a b16 gear set and open diff still not sure if i have the right shim..

Johnny_9

OK. thanks. Also did some research - mainshaft and counter are like two trains on the opposite side of the track; they push against and away from each other in opposite directions.

If the m/s thrust clearance is not right, gear can pop out or "catch" - please add your views as I am still a newbie on this topic

Each cost USD10 each and there are 30 shim sizes; so unless you have pre-measured before, you will have to fork out a tidy sum.

Aquafina

iTrader: (3)

MS shim clearance, integrity of the snap ring/top bearing, and gear heights/spacing is what keeps the MS/CS gears from chewing each other up.

Get a general idea of what size shim you need and order a few within the range.

David @ Synchrotech

iTrader: (1)

Unless you are changing the mainshaft or a case you will not usually need to change the shim. However you should always check the clearance with your current shims and adjust if needed.

TwotoneC1Da9

^ is there a way to measure?

David @ Synchrotech

iTrader: (1)

Check the clearance using a mainshaft holder and dial indicator. The factory service manual shows this procedure step by step.

Johnny_9

does synchrotech have S80/S4C carbon 3/4 synchros, with the "normal" as opposed to the "aggressive" angle? I find the 3/4 abit to aggressive for town street - really need to match the revs......great for WOT shifts though, which i dont do often.

David @ Synchrotech

iTrader: (1)

I'm not sure what you mean by "normal angle"

Johnny_9

sorry was confusing with another vendor (MF??????) carbon synchros where they advise their carbon synchro (pads)

"More aggressive lock angle for effortless high rpm shifting"

. is ST carbon synchro lock angle "stock"/"normal?

TwotoneC1Da9

Good stuff, I only have a haines manuel I'll have to check in there if not I'll take a trip to honda. thanks

David @ Synchrotech

iTrader: (1)

Our carbon synchros are the same as MF. If you want a less aggressive synchro then I would suggest the OEM brass synchros.

Johnny_9

OK thanks. I checked by rpm drop with gearcalc 3rd to 4th = 1,400 rpm; after a bit of practice, i can rev match the shift better. after the overhaul my "foot" forgot the throttle modulation for each gear

Honda Bull

What on earth are you talking about, Johnny 9? lol

Johnny_9

read "how to performance drive a porsche" by motobooks - there is a chapter on shifting - timing the throttle off/on with the synchro engagement; if u use aggressive lock synchros (with racing clutch), your rev matching as you engage the synchro needs to be more precise in town driving.

Aquafina

iTrader: (3)

No need to rev match while upshifting as you can't rev up to a lower RPM. If the RPM is dropping too much (during the shift) when upshifting then you need to shift faster. I use a 7.5lb flywheel, 6-puck unsprung clutch, and MFactory close gear set and I don't have a problem with the RPM dropping too much during upshifts.

Honda Bull

Modern synchronizers aren't really a give-and-take relationship when it comes to shifting for most engines. If it can operate at high rpm and high speeds (which Honda synchronizers work very well IMO), it can operate at low rpm and low speeds.

You shouldn't be using any throttle DURING the synchronizer engagement. The clutch should be depressed to allow for the gear change, and that limits what the engine will do DURING synchronizer engagement. You can be full throttle during an upshift, but by using the clutch, you've disconnected the engine from the transmission, which means the engine isn't doing anything during the synchronizer engagement.

If you are referring to double clutch match revving:
1. You don't do that upshifting.
2. Downshifting in our FWD transmissions where 1-2 is on the countershaft and 3-5 or 6 is located on the mainshaft, you'll find that the engine has little control over 3rd-4th (or sometimes 5th with a 6-speed) gear synchronizer activity. Because, of those gears, the gear's rotating speed you will be selecting next will be determined by countershaft speed given that the synchronizer gear is free spinning on the mainshaft (and as such, is having its rpm controlled by its countershaft partner gear, which is controlled by vehicle speed/differential speed).

The rev matching certainly smooths over clutch engagement on down shifts.

Johnny_9

Town driving with lightened flywheel at a "normal" (not fast as you can) shift speed.

Unless you have the co-ordination of keiichi tsuchiya, on the clutch, throttle and stick (which I am working on), for relaxed town upshifting i dont fully let off the gas, but hold the throttle at the lower rpm for the next gear, while clutching and shifting - e.g my rpm 2nd-3rd is 2000 rpm drop, 3-4 is 1400 rpm (i.e. shorter 4th). note I am refer to town driving not shifting at WOT

If your rpm drop are "stock", yes, your shift speed can be more or less the same from 2-to-5.


also what's the theory why you can shift faster with a carbon clutch?


but while we are on the subject, when do you guys exactly lift off the throttle and throttle on, versus the timing dipping the clutch and moving the stick out of gear, neutral and into gear? i.e just what is your shift technique? do you keep you left foot poised over the clutch and punch it super quick? do u let off the gas completely or partially?

Honda Bull

So... all of what you were talking about with "aggressive locking synchros" was just a light flywheel???

Clutches don't allow you to shift faster. They are meant to harness the torque the engine produces.

Johnny_9

Clutches don't allow you to shift faster. .....................__________________

Johnny_9

[QUOTE=Honda Bull;44773378]So... all of what you were talking about with "aggressive locking synchros" was just a light flywheel???

http://www.youtube.com/watch?v=elvnEP27Qt0

Something like this?

Aquafina

iTrader: (3)

A lighter clutch doesn't let you shift faster, but it will help with high RPM shifting. The synchro, gear, and slider can only physically work so fast, it is possible to shift faster than they can work which will cause a grind. A lighter clutch won't fix this.

The PPG video is out of context in this thread as its showing dog engagement, which does not use synchros.