It's been a long time since I've rebuilt a manual transmission. Problem is that at the end of long straights in my turbo ITR when I am in 5th gear and need to downshift into 4th, lever will just not go into 4th and blocks in neutral. If I double clutch, I can get it to go down to 4th. There are no grinding noises, just gear lever refuses to go into gear. This seemed to coincide with a clutch/pressure plate change, but I am thinking that is a coincidence, maybe. All other shifts are fine, either up or down, with no grinding or balking, as if transmission was new. 5th down to 4th problem happens at any speed. Transmission is original and has never been opened.

Does anyone know what parts need to be replaced? I found this nice DIY B-series transmission rebuild:

https://honda-tech.com/forums/transmission-drivetrain-127/b-series-transmission-teardown-rebuild-tutorial-2443459/

 

I ran into this issue with the original trans in my SI gearbox. It was absolutely aggravating. After pulling the cluster apart I found a needle bearing that had disintegrated was causing issues with the shift collar slipping between the two gears. After cleaning it out and replacing it, problem solved. But make sure you pic up the pieces that got scattered all through the trans. It didn't hurt the trans, just frustrating as hell.

Use Honda pieces and it should be good.

 

I just went through a similar problem on my ITR trans. I could not go into 1st after coming back off the track. Turned out to be a split synchro that would spread out as soon as any pressure was applied. When it would spread it would act like I was being blocked from that gear.

Can you get it into forth with the engine off? Also, how does the 3-4 feel?

 

Just checked. With the engine off the transmission lever moves easily from any gear to any other gear. With engine running and driving, 3-4 feels fine, no problems. Only issue is 5th down to 4th.

 

Id ask James from Gearspeed... he can help you figure this one out.
I had shifting issues too with my ITR tranny.
Left my tranny him to sort out, not it shifts like butttah!

 

There are some good ideas mentioned above. You may have a worn 5-R selector set that is giving you grief, worn shift change assembly, or if the transmission has been run low on fluid in the past it could have damaged the 5-R parts as well.

Typically a clutch issue will be in all gears but, I wouldn't rule it out right away either. Since the trans hasn't been opened yet, it may be a good time to get into it and refresh it.

 

I'm leaning towards a synchro but also check if they machine the flywheel to much the springs on the clutch can hit the flywheel. Although I had that happen with h22

 

A few years ago I partly destroyed my OEM clutch disc with the springs falling out of the carrier, so I bought an Exedy flywheel and a high torque Clutchmasters clutch and pressure plate assembly. I had my mechanic install the clutch, and immediately after that I had trouble downshifting from 5th to 4th. Called them and they said to adjust the pedal which I figured doesn't do much on a hydraulic clutch. Didn't solve the problem. Then a year or so later the engine expired from a stuck wastegate. When I took the clutch off, it was evident the springs on the clutch disc had been rubbing on the inside of the pressure plate fingers, as disc was too thick or improperly designed. I called Clutchmasters again and they had me return the flywheel and clutch assembly. They checked the flywheel and it had the proper step of 0.100", and they replaced the entire clutch assembly with a new model. I put that in after I rebuilt the engine and I have the same problem, perhaps not quite as bad. I have been driving around the problem for a long time, and now I would like to fix it.

Transmission was never low on oil, and I rarely miss a shift, or grind the gears. When I put the tranny back in after the re-build, I had figured there was no need to open the tranny as I assumed the new clutch assembly would fix the problem. But no other shifts are a problem, either with the original Clutchmasters assembly or with the new one. When I was at the PRI show, I asked a tech guy at the ACT clutch booth if the clutch assembly could be causing the problem and he said a clutch problem would affect all gears, not just 5th to 4th. Only thing that nags at me is the problem started immediately when the new flywheel and clutch assembly went in. Perhaps a coincidence. Car has 210 ft-lbs of torque at the wheels on a Mustang dyno.

 

This has the signs of an internal issue.
Time to open it up.