mine shifts fine, but sounds like straight cut gears...

 

Making progress. Got the FM brace, mid pipe and driveshaft out, I really hope I can remove the box without taking the headers off:

 

Got the box out today, but had to remove the headers which meant taking the JRSC off. Maybe I should just replace it with a Chinacharger while it's out.

 

I would

 

Ah, you just have unrealistic expectations! It's a lightweight, aluminum cased trans! The Miata 5 speed holds up a lot better to engine power increases than a stock T5/World Class T5 does (Ford deliberately pulled tip-in ignition timing in the 94+ Mustangs to try and limit all the warranty claims they were getting on stock 5spd 225hp V8s). Granted, it's not bulletproof like an old Ford T&C Toploader 4 spd or Mopar hemi 4spd (both with substantial cast iron cases) but you can usually pickup a spare for $200. I suspect a lot of Miata 5 spds have failed because of poor maintenance too; running low fluid levels, improper fluid types, failure to do regular fluid changes and failure to perform maintenance when trans initially gets noisy or has shifting problems. Either fix the trans when it first gets noisy (Given the relative difficulty and cost of tearing one down to replace syncros, forks and bearings, it is cheaper and faster to go the used route...may not be more reliable in the long term) or buy a cheap spare and drive it until it dies.

BTW, you're dreaming if you think the stock T56 behind an F body LS-1 is more reliable than a Miata 5 speed behind a stock 1.8L. Two trips to the dragstrip with ET Streets were all it took to trash the T56 on my nephew's stock Z28...the T56 does NOT hold up well to powershifts even at stock LS-1 power levels.