psteng19

Starting from a standstill, I accelerate semi-hard revving it up to probably 5k, then I see that I have to avoid an oncoming car at the intersection, so I do a REALLY quick shift and slam it to 2nd, and right as I'm entering the gate (BEFORE I let the clutch out), I hear a CRUNCH noise and feel some resistance/vibration through the shifter.

I'm thinking there's no way it can be grinding a gear since I didn't even clutch out yet.
I've been driving stick for 5 years and have never grinded, so I don't even know how griding is supposed to sound.
Actually, to give a good description/feel of it, I would say it felt like shifting into Reverse while the car is still rolling forward a bit.
So is that the synchros?

The good news is the tranny felt fine afterwards.

2006, 6MT, 17k miles if it makes a difference.

curls

Pretty much everyone I know with a 6MT TSX experiences the "crunchy" 1-2 shift. You only really get it when shifting quickly, and my guess is yes, the synchros have to do a lot of work between 1-2 because the gear ratios are very far apart on those two gears.

If you do a slight pause in between 1 and 2, you'll avoid the crunch altogether.

Oh, and with a short shifter (like me), you get the crunch more often unless you really try to space the 1-2 shift out mentally.

zidenx

iTrader: (1)

yeah i get that crunch/grind whenever i shift to quickly into second.

moda_way

I don't get the crunch at all and I have the 04 6MT. Just takes some getting used to and as curls said, a millisecond more of a pause between gears. I also noticed more smooth engagement with new tranny fluid.

vthree

iTrader: (1)

i never get that crunch at all. even when i eh hem. race from a standstill.. [sigh most of the time lose until hondata comes]

psteng19

Well, it's reassuring to hear that I'm not the only experiencing this "crunch" during the 1->2 shift.

moda_way

If it happens all the time, I'd seriously look at altering your shifting habits.

Mskierki

When you shift into reverse while still rolling you are grinding the gears. The bragging about five years had a good run.

itsme27

I noticed that with this car, shifting into reverse while the car is still moving grinds the gears. I dont remember that happening with the other mt that i used to drive, unless i was high on something the whole time. I miss not having to fully stop to put it in reverse, just a little.

LukeaTron

That's going to happen in any car. If the car is moving, the counter shaft which is always spinning with the wheels, no matter what you do with the clutch, is going to be moving. Reverse involves a sliding a straight cut gear over to engage the drive shaft. This third shaft is always connected to the counter shaft and means that if the wheels are moving forward, the third shaft is moving in the opposite direction of the drive shaft. It's just a straight cut gear (that's why reverse is so whiny), there's no synchro, so if the wheels are moving, it's going grind the flat edges of the gears together until the teeth slip together with an unhealthy clunk.

Moral of the story, don't be moving, especially forward, when you shift into reverse.

Mskierki

There are a few automobiles that utilize a syncro for the reverse gear.

I know that some VWs have one.

psteng19

First time it's happened in a year and a half.

moda_way

Then I wouldn't worry too much. I'm not entirely impressed by Honda's MTF.

rb1

My 1-2 shift has been iffy since day one, especially when the transmission is cold.

It's worst downshifting into 2nd on a turn (I don't double-clutch - typically I clutch just before the turn and shift into 2nd just afterwards), and also, paradoxically, seems rougher the more conservative I'm driving. Shifting 1-2 at 3000 RPM = rough. Shifting 1-2 at 4000 RPM = drops right it.

I think there is some drag on the input shaft even with the clutch in -- even shifts into 5th and 6th don't feel very smooth at first. After I've been driving a few minutes, it gets much better.

Icculus

This is true - I believe most 5MT cars use reverse syncros with helical cut gears. With a 5MT there is an open spot in the 5th gear linkage for a syncrod reverse on the input/output shafts. In a 6MT there has to be a whole additional linkage to the transmission, an unsychronized straight cut is probably the cheapest, easiest, and lightest way to have reverse.

psteng19

I find the same to be true for the 2->3.
The higher the revs, the smoother the shift for these.

Mskierki

I am not quite sure what you are saying here. I don't see what a whole other linkage has to do with the 6th gear and the type of cut on the reverse gear.

But, I don't want to argue with the great and knowledgeable Icculus.

aaronng

We get a new Honda MTF here in Australia. We used to get them in bottles labelled Honda MTF Plus, made in USA. The new ones are Honda MTF 06 and made in Australia. The fluid itself is grey in colour, not golden anymore. It helps a lot with the 1-2 shift.

aaronng

And Alfas.

Icculus

Haha nice, I'm flattered. What I mean is (if in fact I am correct), There are two gears per linkage (back and forth on the stick), with an existing linkage its easy to incorporate a reverse constant mesh helical gear in the open slot, which would not make the whining sound and engage smoothly with synchronizers. With a whole new linkage that has to be added for a reverse gear when there's a sixth, the easiest thing to do is to add an unsynchronized straight cut gear. This is probably the approach Honda took just trying to keep the cost down.

LukeaTron

Reverse always needs it's own shaft. Otherwise it wouldn't be reverse. I don't think the transmission would be all that happy about trying to spin in opposite directions at the same time.

I've never seen a reverse gear work any other way than what I described (straight cut gear that slides axially) though it wouldn't be surprising that Alpha Romero decided to do it differently, just to be different.

I also don't really understand why you would want a syncho on the reverse. How often are you going to be shifting into reverse while on the move? I'm not saying they don't exist, I just don't see why you would bother.

Mskierki

It makes it easier and smoother to shift into gear. Just like the syncros on forward gears 1-6.

LukeaTron

But neither gear should be spinning when you're shifting into reverse. 1st through 6th have synchros because the gears (well, dogs) are spinning at different rates. The synchros bring the speeds together so it doesn't catch suddenly when the dogs engage.

rb1

They exist simply because you avoid grinding gears (and hence damaging the transmission) while shifting into Reverse when moving.

They are comparatively uncommon, but not unusual on high-end cars equipped with manual transmissions.

The Audi S4 had one a few years ago... (http://www.audiworld.com/model/s4/01/specs.shtml)

Mskierki

Your right neither gear SHOULD be rotating. But, as it has been mentioned, sometimes they are and that is not good for the transmission. It is possible to have transmissions that do not have syncros and you have to match input to output shaft speeds by double clutching and engine speed matching. Having the syncros there not only makes that technique unnecessary but it also makes for a smoother shift. Ever driven a tractor? It is not a smooth shift at all!