Grinding when shifting 1-2 in Miata

99 Miata 10AE (6 speed). I just got it, and a lot of the times when I shift 1-2 it will grind unless I do it really fast. It sometimes does it 2-3. If I shift really fast, like an autocross, there are no problems, but if I do it like I normally drive on the street, it will grind for a second before it will go in. I haven't driven it enough to notice if it stops when it gets warm or anything, and I don't know when the transmission fluid was last changed. I assume that would be a good place to start? Or is the Synchro just completely warn out?

For now I'm just shifting really fast. Any suggestions/thoughts?

I'd change the fluid, that's always made a difference in the Miatas I've had. Also, does the 6-speed have the little 'turret' around the shifter that eventually runs dry? You might want to check that, too.

BTW, does it grind on downshifts, too, when you don't double declutch?

If the syncros were worn, I would've thought shifting fast would only make it worse.

Could it be the clutch needs adjusting?

Isn't the clutch hydraulic on NBs, too? Or is that only the case on NAs?

If it's hydraulic, it might want a new slave cylinder...

BoxheadTim wrote: Isn't the clutch hydraulic on NBs, too? Or is that only the case on NAs? If it's hydraulic, it might want a new slave cylinder...

Do both the slave and master at once. Not much more money and you'll only have to bleed it one time. Besides whenever I do one alone the other is not far behind. Add a braided clutch line and you'll never have to touch it again.

The masters don't have anywhere near the failure rate the slaves do. A good check for the hydraulics is to see if there's any drag on the disc - it is hard to slip into 1st gear when you're at a stop?

The 6-speed does not have a separate reservoir in the turret, don't try to fill it unless you want to fill the transmission right to the top

When you drain and refill the trans I recommend Redline MT90. I use that on my 5-speed car and it makes a noticeable difference in smoothness.

I like MTL for street cars, MT90 for track cars. The MTL works a bit better in cold temperatures.

I really don't know most of the answers to the questions you've asked, I haven't driven it enough to notice. I'll start paying attention as I drive it more and bring this thread back.

Keith, what about a Daily Driver that really only gets driven about 3 times a week (but that could fluctuate significantly up or down), autocrossed about 2-3 times a month from March-November, and lives in Northern Illinois (pretty hot in summer, really cold in winter)?