Lust
Senior Member
- First Name
- Michael
- Joined
- Apr 17, 2018
- Threads
- 16
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- 1,411
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- 1,777
- Location
- Bay Area
- Vehicle(s)
- 2019 Champ White Type R
- Thread starter
- #1
Hi all,
I see too many new threads or posts about 2nd gear grinds and 4th gear lockouts. Instead of taking time to constantly write something out, I'm just going to refer people to this post instead. Below I will explain the causes and solutions of our transmission's woes.
2nd Gear Grinds
This is probably the most common "issue" in our transmission. The 1st to 2nd shift is very harsh on the synchros due to the difference in gear ratio.
For reference:
1st gear: 3.625
2nd gear: 2.115
3rd gear: 1.529
4th gear: 1.125
5th gear: 0.911
6th gear: 0.735
Reverse: 3.758
Final Drive: 4.11
As you can see, the jump from 1st to 2nd is significantly larger than the other gears. This means the 2nd gear synchro will need more time to synchronize the gear. The gear grind is exacerbated from incorrect clutch adjustment from factory and poor driving technique. Factory MTF, (Manual Transmission Fluid), is fine in most cases as it is formulated specifically for the transmission. It is extremely rare that a transmission is "out of spec" or has a defect.
The clutch pedal free play varies greatly from car to car. I've personally experienced this owning 2 FK8s and being in and out of a dozen friends' cars. A poorly adjusted clutch pedal will cause slow clutch release and the clutch will drag because there's not enough pedal stroke to fully release the clutch. By eliminating unnecessary pedal free play, we ensure the clutch is fully disengaged as quickly as possible. A common misconception is the CDV (Clutch Delay Valve) located in the slave is delaying/slowing the release of the clutch. This is simply not true. The CDV located in the slave is designed as a one way valve to slow the engagement of the clutch to reduce driveline shock. Not the other way around.
Illustration of the CDV located in the slave from Honda
Poor technique also comes into play as I see most inexperienced drivers start to move the gear lever before their foot is fully on the ground. The grind becomes more frequent if the clutch pedal is poorly adjusted. The synchro simply can't keep up at this point and it causes a grind. The best technique is to fully depress the clutch before applying any pressure to the gear selector.
Gear Lockouts
Typically the 4th gear lockout is due to the shifter gates not properly lining up. Since the shifter isn't directly bolted to the transmission, there are several more linkages and they have some tolerance/slack to aid in lower NVH. The downside is the shifter doesn't feel as precise which makes it easier to improperly move the shifter into the gate or in this case moving the gear selector in between gates. Technique is also important as I've seen many people move the gear lever in diagonal lines which makes it easier to miss the gate.
A poorly adjusted clutch pedal can also cause gear lockouts but it is not as common.
1st gear and reverse lockouts are actually normal due to the mechanics and design of the gears/synchros.
Solutions
The first thing I recommend to anyone is to adjust the free play in their clutch pedal. It is more of a trial and error thing so don't be upset if you don't get it right the first time. The two things we adjust are the amount of pedal travel / stroke and the amount of dead space before the clutch actually starts to disengage. The key here is to optimize the clutch hydraulics to move as much fluid as quickly as possible. This makes the clutch disengage fully and quickly giving the synchros the appropriate amount of time to do their job.
Second solution is to upgrade the CMC (Clutch Master Cylinder). Eman AKA k20z3allmotor makes modified OEM CMCs that have a deleted damper and an enlarged feed hole to aid in more fluid transfer. Again, the goal here is to optimize the clutch hydraulics system to get the clutch disengaged as quickly as possible. This will require you to bleed the clutch line and would kill 2 birds with 1 stone to ensure no air is in the clutch line.
Link to purchase:
https://www.naperformanceftw.com/kzcmc/kzcmc-clutch-master-for-honda-civic
Third solution would be to experiment with different MTFs. Each transmission is built to fine tolerances but not always the same. Different brands have different additive packs, friction modifiers, and viscosities. Changing the MTF could have positive effects in synchronizer performance and overall shifting feel.
Recommended gear oils:
Parts I personally recommend
Video Tutorials
Clutch Adjustment
Clutch hydraulics explained by a prestigious transmission builder
Manual Transmission Driving Techniques
I see too many new threads or posts about 2nd gear grinds and 4th gear lockouts. Instead of taking time to constantly write something out, I'm just going to refer people to this post instead. Below I will explain the causes and solutions of our transmission's woes.
2nd Gear Grinds
This is probably the most common "issue" in our transmission. The 1st to 2nd shift is very harsh on the synchros due to the difference in gear ratio.
For reference:
1st gear: 3.625
2nd gear: 2.115
3rd gear: 1.529
4th gear: 1.125
5th gear: 0.911
6th gear: 0.735
Reverse: 3.758
Final Drive: 4.11
As you can see, the jump from 1st to 2nd is significantly larger than the other gears. This means the 2nd gear synchro will need more time to synchronize the gear. The gear grind is exacerbated from incorrect clutch adjustment from factory and poor driving technique. Factory MTF, (Manual Transmission Fluid), is fine in most cases as it is formulated specifically for the transmission. It is extremely rare that a transmission is "out of spec" or has a defect.
The clutch pedal free play varies greatly from car to car. I've personally experienced this owning 2 FK8s and being in and out of a dozen friends' cars. A poorly adjusted clutch pedal will cause slow clutch release and the clutch will drag because there's not enough pedal stroke to fully release the clutch. By eliminating unnecessary pedal free play, we ensure the clutch is fully disengaged as quickly as possible. A common misconception is the CDV (Clutch Delay Valve) located in the slave is delaying/slowing the release of the clutch. This is simply not true. The CDV located in the slave is designed as a one way valve to slow the engagement of the clutch to reduce driveline shock. Not the other way around.
Illustration of the CDV located in the slave from Honda
Poor technique also comes into play as I see most inexperienced drivers start to move the gear lever before their foot is fully on the ground. The grind becomes more frequent if the clutch pedal is poorly adjusted. The synchro simply can't keep up at this point and it causes a grind. The best technique is to fully depress the clutch before applying any pressure to the gear selector.
Gear Lockouts
Typically the 4th gear lockout is due to the shifter gates not properly lining up. Since the shifter isn't directly bolted to the transmission, there are several more linkages and they have some tolerance/slack to aid in lower NVH. The downside is the shifter doesn't feel as precise which makes it easier to improperly move the shifter into the gate or in this case moving the gear selector in between gates. Technique is also important as I've seen many people move the gear lever in diagonal lines which makes it easier to miss the gate.
A poorly adjusted clutch pedal can also cause gear lockouts but it is not as common.
1st gear and reverse lockouts are actually normal due to the mechanics and design of the gears/synchros.
Solutions
The first thing I recommend to anyone is to adjust the free play in their clutch pedal. It is more of a trial and error thing so don't be upset if you don't get it right the first time. The two things we adjust are the amount of pedal travel / stroke and the amount of dead space before the clutch actually starts to disengage. The key here is to optimize the clutch hydraulics to move as much fluid as quickly as possible. This makes the clutch disengage fully and quickly giving the synchros the appropriate amount of time to do their job.
Second solution is to upgrade the CMC (Clutch Master Cylinder). Eman AKA k20z3allmotor makes modified OEM CMCs that have a deleted damper and an enlarged feed hole to aid in more fluid transfer. Again, the goal here is to optimize the clutch hydraulics system to get the clutch disengaged as quickly as possible. This will require you to bleed the clutch line and would kill 2 birds with 1 stone to ensure no air is in the clutch line.
Link to purchase:
https://www.naperformanceftw.com/kzcmc/kzcmc-clutch-master-for-honda-civic
Third solution would be to experiment with different MTFs. Each transmission is built to fine tolerances but not always the same. Different brands have different additive packs, friction modifiers, and viscosities. Changing the MTF could have positive effects in synchronizer performance and overall shifting feel.
Recommended gear oils:
- AC Delco / GM Synchromesh Friction Modified - make sure to get the friction modified version.
- Amsoil Synchromesh - really inconsistent oil. Some have had better shift feel and others worse.
- Motul Gear 300 - great for heavily tracked cars. Do not use the LS version.
Parts I personally recommend
- Acuity Shifter Cable Bushings - for more precise feel
- Acuity Stage 3 Short Shifter - full adjustability and stronger centering spring allows for more precise gate selection
- Acuity Rocker Arm - if using OEM shift assembly
- Acuity Centering Spring - if using OEM shift assembly
- Hybrid Racing Shifter Cable Bushings - intended to be used with their short shifter kit
- Hybrid Racing Short Shifter - more of an OEM feel compared to Acuity meaning softer and more slop
- Hasport Rear Motor Mount - This will help secure the transmission and reduce movement to allow for more precise gear selection
Video Tutorials
Clutch Adjustment
Clutch hydraulics explained by a prestigious transmission builder
Manual Transmission Driving Techniques
Sponsored
