Saki GT

As I talk with more and more people about the character of the S2000 and its shifting, I keep coming across the same basic thoughts.

When new, the shift action is rifle-bolt slick and direct, with minimal effort to change gears
As the miles accumulate, the action becomes more course but still direct
Eventually, shifts become balky and it feels like you are shifting over a hump or spur regardless of gear

The behavior is similar to this:



Where the level of effort to get into the selected gear gradually rises over time. Its not wrong per se, but not as smooth as when new or when a transmission has been freshly serviced.

From all I've read and discussed to date, this behavior is caused by the input spline as it loses lubrication over time and use. Honda did not use enough grease at the factory for the lubrication to last beyond ~40k mi. The "bump" in resistance is the spline rubbing against the gearset and not sliding like it used to, right? Regreasing it while the transmission is apart (for a clutch job, lets say) is the solution.

Is this correct thinking? Thoughts?

jordaninabox

Makes sense to me, luckily I have not reached this point (mile wise) to be able to notice it. But I am interested in what others have to say. If this is the case im not looking foward to it, any input on how to keep it from happening?

SpitfireS

It is an open (unsealed) greased spline where clutch dust accumulates.
Also, grease will harden over time, especially when its hot.
Grease is a "solid" lubricant (named soap) & oil, the two will seperate over time.
And then there is rust.
All combined (grease seperating, rust and clutch dust) you end up with a hard compound that is not like grease, more like glue.
The clutch disk also has splines, it rides on the trans input shaft.
The splines allow it to slide (when needed) and transfer torque (when needed) without any action.
A sticky disk (old rusty grease on the splines etc) will not allow the disk to slide as easy.
So when you press the clutch pedal and move the pressure plate away from the disk the disk will not break free from the flywheel by itself, it needs a little nudge.
That nudge is you shifting into the next gear.
So you feel the resistance as the synchro has to break the disk free from the flywheel, needed because of the difference in rpm.
The harder the disk slides the more crunch you feel.
Yes.
As a last resort.
When you are 100% sure the clutch hydraulics are 100%.
You know, the famous air-in-clutch-slave and clutch pedal mechanical freeplay etc.

And you have not even mentioned the foot-hand coordination.
"Shifting hard" sounds cool on the web (you racing driver yo!) but it's most likely you messing up the shifts.

"You" not necessarily the OP

Saki GT

Thanks for the explanation.

Basically its a characteristic one can feel when simply moving the shifter between gates, say back and forth between 3-4. Even without releasing the clutch pedal, just moving the shifter, there is always a bump in effort. Would that be more in line with the input spline or some other part?

What specifically would cause friction or resistance when simply moving the shifter back and forth between say 3 and 4 and not engaging the drivetrain?

acn684

^^ I have very similiar symptoms as Saki. Even with engine cold, sometimes the shifting between gears is "notchty."

Like you said, my 3-4 cold engine/off engine is occasionally notchy.

Weirdly, my 2-3 cold is smooth but then my 2-3 warm can be notchy.

Saki GT

Yes let me add, this is when the engine is off as well as on, so I wouldn't blame it on heat, fluid, synchros, etc. I'm trying to figure out what basic component might be causing resistance.

zeroptzero

I think it makes sense to stiffen up over time, things are never as good as when the car leaves the factory, but lots of s2k's have gone over 100k miles on the factory clutch without shifting issues.

I know doing the shifter lube TSB really made an improvement on my car, I know this is a totally differnet issue than the clutch/tranny spline matter, but it does help in its own way. My ap1 has 60k on it, the shifter has been lubed twice and it feels pretty much perfect. This won't cure the dry spline issue but it is beneficial nonetheless.

SpitfireS

There are (at least) 7 springloaded balls that catch notches in the shift rods.
You will always feel that when you shift, especially when shifting between (your example 3-4) gears with engine off / not moving / clutch in.
The synchro's line up during the first shift, the next time you only feel the resistance to push/pull the shift rods out of their locked position.
Locked by springloaded balls.

The input shaft splines only come into play during shifting while driving.
If the clutch disk doesn't break free from the flywheel by itself it stays at crank rpm until the synchro tries to slow it down or speed it up.

Saki GT

The only thing I can think of is the syncros getting stiffer over time and not sliding out of the collars as smoothly as when new. I've never seen an S2000 transmission pulled apart after some use. Maybe the carbon synchros wear in a particular manner vs the brass of the AP1s.

Do those spring loaded balls get greased as well? Could the synchros be getting sticky or misaligned?

Blindeye_03

Shifting was pretty stiff on my 08 with 40k miles till tonight after a buddy helped me change my transmission and diff fluid. All I can say is night and day difference .