Ok, so driving the car home the other night, you could definitely hear the gear box whirring as it drove along - not a "noise" or "whine", just the whirring of the gear box. Normal?
Second question, are there any gearbox fluids that should NOT be used in a Miata? In the add, the PO mentioned he'd changed the fluids; I know for the old Z-cars, there was a particular type that should not be used as the "metallurgy" was bad for the syncros.
If there is something "not good" for it, I'll be adding a fluid swap to the couple other knick knacks the car needs.
Yes they have brass syncros. There's bad fluid.
I can hear the transmission in all of mine. Especially 1st gear.
Old Land Rovers need specific fluids or the synchros start to come apart.
As for the Miata, fill it with Redline MTL (street car) or MT-90 (track car) and stop worrying.
I do love MTL; thanks fellas.
beans
Dork
1/30/15 3:59 p.m.
My '95R made a whining noise in 1-4(4th was LOUD, like almost straight cut loud) after I dropped in a junkyard box from a '92. I swear 2nd gear was shorter, too.
Turns out miata 'boxes don't like powershifting though.
If the shifter gasket/lower boot is torn at all that will also let A LOT of noise in. I was amazed at how much things quieted down (relatively speaking of course) when I swapped in a new one.
The good news is a full shift turret rebuild and fluid change is relatively cheap (seems to me it was well under $100 for the whole thing) and is a great Saturday afternoon project. There's a decent chance your car is due for it. If you are feeling any slop in the shifter, do both.
There's also a trans fluid option from Ford Motorsports that works, which is what I used because I could get it locally. I've read reviews from people who have tried both, and the consensus seems to be the Redline fluid is better.
Fluid preference depends on which forum you ask. 
