BroxS2K

My 85k-mile AP1 started crunching going into 4th this past weekend at a HPDE. Only crunches during high-RPM shifts; it shifted fine on the drive back from the track. It's mostly a track car at this point but will always drive to and from the track with it. It's still a stock engine though it's likely getting supercharged and running mild boost next season.

With the plans for it and how it's being used, what would you recommend in terms of dealing with the transmission? Find a used one off of car-parts.com, rebuild the current one with new synchros, cryotreat the gears...?

Chibo

Change the fluid before you write it off. What you're describing is pretty common for most of us and it is a sign we pushed the fluid change interval too long.

BroxS2K

Thanks for the input. I will try that. I had replaced the trans fluid with Honda MTF a year and about 7k miles ago. The fluid probably has broken down after about 8 track weekends.

S2000_916

Change the slave fluid also

spaded.racer

Also, have you checked your motor and trans mounts?

s2000Junky

Yeah make sure its not the clutch as well. Fluid gets hot and you might not be disengaging the clutch all the way via the clutch slave or master cylinder after things heat up. I recommended before track day you do a clutch fluid change/bleed with your high temp brake fluid, make sure clutch pedal is adjusted properly and no air in the line. A SS clutch line isn't a bad idea either for cheap insurance. I thought I was having trans issues on track in past and turned out to be the clutch hydraulics.

BlueBarchetta

It’s likely one of the above things will fix it. However, if it doesn’t, this issue was an early indication of my clutch throw out bearing going bad. Not an easy fix but I still think it wouldn’t be a synchro

BroxS2K

But if it were the result of the fluid being too hot and/or the clutch not engaging entirely one would think that it would crunch into EVERY go, no? I'm going ahead and replacing the trans fluid (currently Honda MTF) with Royal Purple Synchromesh and also replace the clutch fluid with fingers crossed.

roel03

My car does the same thing at the end of a 20 minute session, and only going into 4th. It's usually when the fluid overheats because if I do a cool down lap it goes away. I also use Honda MTF and replace it once a year.

freq

Gear sets new aren't cheap and it's a ton of work just to get to them.

At that point, replace the clutch and the trans w/ a known good unit.