Grinding all gears... not the clutch?
 

MY PROBLEM: I seem to be grinding gears about 1 of 20 shifts randomly. When I shift, the clutch is to the floor (I have been driving a multitude of manual cars for over 10 years), so I am certain that it's not my driving. I have tried shifting slow, fast, gentle pressure, waiting a second after pushing the clutch in, and every other shifting technique I could think of to let the synchronizers do their job. The grinding still happens with about the same frequency no matter what I do. It happens with all gears, which would usually point to the clutch. However, it seems like the clutch is disengaging just fine: I can shift into reverse no problem. When I'm cruising and push the clutch in, the revs immediately drop. I can free rev in-gear with the clutch pressed in. The car doesn't move forward at all with the clutch pressed in while in gear at a stoplight.

THINGS I'VE DONE TO TRY TO FIX THE PROBLEM: clutch pedal adjust, flush and bleed the clutch system, replaced transmission oil with Honda MTF, replaced and greased both shifter bushings.

HYPOTHESIS: Unless the clutch is just slightly engaged but not enough to prevent the revs from dropping (when I'm cruising and push the pedal down, for example), then it has to be the synchros. Isn't it sort of odd though? I don't usually hear about people having synchro problems in 1st, 2nd, 3rd, 4th, 5th, and 6th all at once! What else can I do to determine if it's the clutch? I'm debating getting a used transmission but I don't want to invest hundreds if it's not the synchros.

Thanks!

Are you up-shifting below 4300 rpm? Try shifting in the 4300-5000 rpm range.

-- Chuck

Could also
remove and grease the clutch fork in gearbox it just pulls off.
grease slave cylinder pushrod,also nipple sometimes needs removal with a file.
also red line in gears more often,it helps settle things out a little ;)

What year is the car?

Thanks for all the suggestions so far. I have tried shifting at low, medium, and high rpm with basically the same results.

I'll try to remove and grease the fork. What's the procedure for that? Disconnect slave cylinder push rod and wiggle it out? I have a lot of "clutch buzz" decelerating from 3500 to 2000 so maybe I should just replace the fork anyways... Noodels, what did you mean by the slave cylinder nipple sometimes needs removing with a file?

I was going to try GM Synchromesh Friction Modified, since I've heard it was originally designed for a GM gearbox with grindy gears. Is Redline even better for tired synchros?

The car is 2000 model year, btw. Oh and I forgot to mention that when the car is cold, it shifts pretty well. The grinding is significantly worse once heated up.

Regarding the transmission fluid, I mentioned that I was going with GM Synchromesh FM or maybe Redline. I'm open to other suggestions for sticky/"frictiony" oil.

The nipple on the end of slave rod needs to be polished when you grease it. Put rod into drill chuck, then use a suff pad while spin drill.

You mentioned clutch pedal adjusted. Did you mean the clutch rod, or the clutch pedal height? Whichever you didn't adjust, try adjusting it.

My theory is the clutch splines are dry, so clutch disk doesn't slide well. Sometimes it does, sometimes it doesn't.

Fix is drop trans, lube everything like you were doing a new clutch. But since you are dropping trans anyway, and since you have clutch buzz, you should just plan to do a new clutch. Disk, release bearing, release bearing guide if needed, possibly pilot bearing. Resurface flywheel and pressure plate.

Thanks for the clarification. I'm doing the work in my driveway so I'd like to avoid dropping the transmission if at all possible. I'll need to think about how/when I could do that. I wonder if there's any remote possibility of getting some sort of spray lubricant into the splines without removing the transmission completely. Then, if I notice improvement, I could do a full clutch job. Also, I only adjusted the clutch rod. The height seemed fine, but I can adjust it anyways just to eliminate that possibility.

I fought problems with my year 2000 transmission for years that was very frustrating especially when the box was hot . This is from when the car was new and Honda was no help. There was a TSB regarding poor shifting back in 2000 (claiming a stacking tolerance problem) but me and few owners that I talked to were not happy with the results and I knew a couple that sold off their cars and swore off Honda products.

It finally crapped out and I bought a transmission that was in a 2002. What a difference! It shifts smoothly every time regardless of temperature and is a pleasure to use. My only regret was waiting so long to replace the transmission. It was a relatively cheap fix and transformed the car.

I think there was a run of bad boxes early in the life of this car and replacement with a later transmission is the only real fix.

this is interesting.

maybe related to the synchros?

did you tear down the original transmission to see what was going on?