I've had the same issues. I'm willing to bet motor mounts could be the blame and it couldn't hurt to change the tyranny fluid.
I had the same problem coming down to 3rd from high 4th and found my rear mount was shot. Replacing it helped.

 

I've had the same issues. I'm willing to bet motor mounts could be the blame and it couldn't hurt to change the tyranny fluid.
I had the same problem coming down to 3rd from high 4th and found my rear mount was shot. Replacing it helped.

I’m gonna try the hybrid cmc/slave first. I’m planning on getting a new rear mount anyways because I want a skunk2 downpipe.

 

It could be that the synchros are messed up due to poor driving technique or abuse usually the latter.

 

I had same issue in 2nd and 4th, I bought a hybrid racing clutch master cylinder and slave cylinder and it worked like a charm.

 

About to buy the hybrid cmc and slave kit. Yeah it only happens in 4th sometimes but everytime in 2nd. I’ll update if it works.

 

Hybrid Racing K Swap Clutch & Slave Cylinder Upgrade

Helps to eliminate grinds during hard shifts Genuine Honda parts - not reproductions Stainless steel braided clutch line Improves the feel of gear changes OEM Slave Cylinder (NON-DAMPENED) Description Vehicle Fitment Technical Data Included Install Guide COMPLETE CLUTCH RELEASE SYSTEM...

www.hybrid-racing.com

 

Anyone on here who has said they were trying the cmc and slave kit have any updates? Has it helped? I’m having the same issue now but only with 2nd gear. And not always. Most of the time it shifts fine into 2nd even when pushing past 6k shifts but every once in a while when I go to grab 2nd, it just doesn’t want to go in. It doesn’t grind, it just won’t go in until I let the revs drop then it goes in again and it’s like it never happened. Any updates would be highly appreciated before I go spending money on stuff I don’t need lol

 

Currently getting my sirimoto cmc/slave kit installed, should have my car back sometime this week, so I’ll keep ya updated on how it works. (KW Supercharger is being installed, that’s why it’ll be a while)

 

CMC & Slave upgrade should fix your problem - do some research, your only other option is take it to a trans shop and have them diagnose it, I think trying the parts would be cheaper esp if you do it yourself! They’re not that expensive.
IF that doesn’t fix it then you know you’ve got bigger problems

 

Yea I really think the cmc and slave will help a lot because it never grinds or has issues going into 2nd when just normally driving. Only when I get a little too aggressive with it and that’s only once in a blue at that.

 

I’ve been having the exact same issue on my si. For anyone else who had the issue does getting the cylinder kit fix it?

 

I will keep you updated, I got my supercharger installed but it’s currently sitting at home with just a basemap tune from my tuner until Mondays dyno tune.
i had a sirimoto cmc/slave kit installed same time as my SC kit so I can’t fully test it out until the cars running right.

 

Sounds like you need a cmc & slave … that engages way to low

 

Sounds like you need a cmc & slave … that engages way to low
[/QUOTE

sounds like this^
New cmc and slave and the engagement point is nowhere near where it used to be and it feels like a whole new car, it’s crazy.
Mine used to be super close to the ground as well, so I was used to that and now it engages better and higher and it feels so much more nat
It’s hard to explain.

100% recommend this kit, sirimoto cmc and slave

 

You didn't test drive the car?

I would check the fluid levels. I had a squeaky clutch peddle a few months ago, a little WD40 took care of it.

 

My dad did and I guess he didn’t catch it or drive it hard enough to catch it. Like I said it’s only NOT going into 2nd at high rpms. Fluids are fine. Any other ideas? might try a clutch adjustment and might check the cables and bushings.

 

Yeah, I'd try a clutch adjustment. Could also be a bad slave cylinder or clutch master cylinder.

 

Mine is the same, in all gears

 

Can u link it to me

 

Been having the same issue for a while now so I figured I’d look into it.

Couple months ago I had my clutch changed to the fx300 clutchmasters kit, so new Honda fluids and all that too.

installing my new cmc/slave kit soon

My car shifts fine out of gear in every one but 2nd to 3rd when I am at 7000+ rpm, and it just doesn’t let me get out of 2nd until the rpm’s drop to about 6kish and then I can put into 3rd. I’ve learned to time it properly and I do a smooth shift to 3rd but I’m really hoping it’s just a cmc/slave issue and not synchros, since I baby my car and never redline 1st gear, I start at 3rd most of the time, sometimes 2nd and then that’s when this happens. I figured this was the clutch delay valve everyone talks about but guess not?

(also the guy that owned the car before me seems like a total dumbass and the type of guy that mistreats his cars, since I ended up following him on ig after buying)
Really hoping he didn’t dog it out and mess up any synchros.

 

I am also interested in possible resolutions as I have a 2012 Civic Si with ~93k miles displaying the same issue in multiple gears. When it happens upshifting above ~5k RPM there is no grinding or noises; it's like the shift lever is hitting a solid wall instead of going into gear.

Motor mounts were also my initial guess as it shifts well at lower RPMs. Shifter feel is pretty close to two other 9th Gen Civic Si's that I've owned, both were 2015 model year. I haven't closely inspected all of the motor mounts yet.

I changed the transmission fluid when I bought it a few months ago and that made no difference. I also replaced the shift cable bushings on the transmission side (shift lever side cable bushings feel tight) which had no effect.

My clutch engagement point is also super low (~1 inch off the floor if I had to guess) so I've been meaning to bleed the slave cylinder and see if that helps. Fluid level in the reservoir is fine.

 

My clutch engagement point is also super low (~1 inch off the floor if I had to guess) so I've been meaning to bleed the slave cylinder and see if that helps. Fluid level in the reservoir is fine.

Oh so whoa! A low pedal can definitely cause the type of issue you are describing. I've it happen in cars, as well as on bikes when adjustment was needed to raise the engagement point.