6 speed, 5th gear grind.
 

I get a grind going from 4-5 and from 6-5. Its a lot less pronounced from 4-5, sometimes won't even happen. Anyways, only happens when warm, doesn't really happen when cold. I know theres some additive some people run, can't remember the name of it to save my life. Running Amsoil MTG at the moment. Anyone know the additive I'm talking about/have any ideas on what I should run through this thing to make this shit stop? Was thinking of running something thicker, but don't know if that will help at all.


tl;dr version: 5th gear grind, wat do?

I had a problem with 4-5th grinding for about 6-months...then it went away. I presume that is from the previous owner putting the wrong oil in it. How long has that oil been in the trans?

Its been about 2-3 weeks. I had read about grinds going away out of nowhere...
Guess I'm waiting this one out.

I've heard of miracles happening with GM Syncromesh, tried it myself when I had a Civic and it did work pretty well. Not sure what it could do to a Miata tranny, but I would google it up to check before going about... or just skip 5th gear. :D

Im going to try some GM friction modifier and see what happens. If that doesnt do anything I'll try synchromesh. It seems to be slowly getting better. My tranny shifts so well when its cold, but slowly gets worse when its warm, I don't get it.

All of my shift grinding problems went away after replacing the slave and rebuilding the master cylinders. It turned out to be the master cylinder slowly going, I had the same symptoms and all of a sudden one day the clutch just stopped working. It was always better in the cold as well. I would look into the clutch hydrolics after you try the friction modifiers. I hope this helps.
-Steve

I also rebuilt my master and slave with some success. My grind took months to go away. I run penzoil synchromesh which is a substitute for the Gm stuff in my daily. It's fine in a street car but MTG is a couple bucks for and good for a really long time in a daily.

Rebuild the hydraulics and give the oil a few more months before you panic.

Rebuilt master/slave less than 1000 miles ago when the master died. I do feel that I'm need of a clutch adjustment though, sometimes having the pedal all the way down and putting it into 1st makes the car slightly move forward. I'll try that too.

Ordered a 4 oz bottle of GM stuff and hope all of these things do something before my next track day. :facepalm:

Look on the bright side. The 5th synchro is easy to change.

I just changed my slave and master as well. I found that the system was not fully bled of air by the normal pump and hold process. I actually only got the rest of the air out by opening the bleeder, having my helper slowly press the peddle to the floor then closing the bleeder and repeat. Seems there is something in the system hydraulics that allows air to "hide" when the usual process is used. There is also a U Tube video that shows a trick for getting all the air out of the slave as well. Requires a bit better access to the slave than I can manage without ramps and smaller hands.

I highly recommend you reverse bleed and tap the lines with a hammer while you do it. This will make life much easier.

Hustler, what system do you use to reverse bleed?

-Adjusted clutch pedal
-fresh Amsoil MTG and some GM additive
-track day at Laguna Seca
-Still grinding.
-FUCK

broken Motive bleeder.

Give it time to fix itself. Mine ground for lets say 2 or three track days in 2009, it was fine all of last season and this.

You may want to drain the fluid you have in there to treat it like a flush. I recently had my replacement 6 sp swapped in, then had to remove it again to install a clutch. The MTG was only in there for a few hundred miles. I expected to see a golden fluid drain out (I was going to reuse it) When a saw a gray fluid drain out I was quite surprised. Needless to say I did not reuse the fluid.

I guess I am suggesting to flush the trans, there may be some crap in there.

I has an extra 5th synchro and gear if you want to buy it.