[fireant]

Background:

• I have a 91 CRX Si tranny that was rebuilt in January of '05. It was a stock Si trans with new synchros, exedy oem clutch, throwout bearing, and resurfaced flywheel.
• I have autocrossed it at at least 50 events since then over the last 2 years using 1-2 gears, and 3rd only a few times.
• I have daily driven the car, but not abusively
• Never drag raced
• I've had no horrible misshifts that I can remember
• I have ES motor mount inserts and shifter bushings.
• In December of 05, and just this December I have drained and refilled it with Honda MTF

Problem:
The trans shifts quickly and flawlessly at high revs through all the gears, except 2-to-3 upshifts grind badly unless I let the revs fall to 4250 or so.

This is unexpected since I would expect 1-2 to be problematic from autocrossing, but they are smooth and easy, even above 6000 RPM. I have only used 3rd gear about 4 times in autocrossing over the last few years, so I dont think its been abused on the track. However, I want to do an HPDE or Time Trial this year, and waiting 2 seconds for the revs to fall from 7000 to 4250 is not a good thing...so I want to fix the 2-3 grind problem.

I'd like any input on where to start with troubleshooting this problem... clutch adjustment? shift rod or fork? bad synchro?

Thanks in advance.

 

[ryan89crx]

my guess would be a shift fork

have you thought about trying a different trans fluid to see if it helps?

 

[fireant]

I was hoping the new Honda MTF from just last month would make at least a small difference, but it didnt at all. I'm willing to try anything before I get another rebuild.

 

[ryan89crx]

try some GM Syncromesh(non friction modified) or Penzoil Syncromesh

some people swear by it

 

[BryanK20]

sounds like a fork. how much did the rebuild cost you?

 

[transzex]

How was the tranny before rebuild????

What parts (synchros) were used?

I'm thinking worn 1-2 or 3-4 fork.......

I'm guessing Standard Transmission parts were used and the gear cones not scuffed, nor the shifter fork checked for wear.

Dr. Bone, calling Dr. Bone, trans emergency in room 101...........

 

[fireant]

The trans was rebuilt by effinmotorworks (they still occasionally do some work for locals), and I bought the kit and and new synchros from standard transmission, and the cones were definitely scuffed by Rueben at effin when he did the assembly. I got a very good deal on this trans, and I helped as much as possible on the install.

Now the forks in the trans are a different story. I dont know anything about them, but I'd be willing to bet that's the weak link. The trans was from another crx, and I traded my worn out one in as a core when this one was finished being rebuilt.

Transzex, if the 1-2 fork is bad, does that effect the 2-3 upshift? I ask because like I've said, my car has seen alot of hard 1-2 shifts...and it still takes them quite well.

I have a garage, air, almost every tool imagineable, and I'm mechanically inclined enough to do anything that doesnt require a super-expensive exotic micrometer. Should I be able to fix this? Would I need to replace the shafts? springs?



BTW: Thanks for your help everyone.

 

[transzex]

if they forks are worn, you barely out of 2nd gear when trying to engage 3rd, little time for the synchros to do their job......

basically strip the tranny down and inspect the forks, you'll be able to see the wear....

Also hard 2-1 shifts (autox) will also wear the 1-2 fork and effect 2-3 upshift.

 

[fireant]

OK, I'll look into it... I rarely downshift 2-1, but I bet the 1-2 fork is the problem. Thanks again for your help.