Six speed availability and price and strength, generally?
 

I'm going to be yanking the engine soon, so why not remove the transmission at the same time? I've still got a 5 speed, which I've managed to break once or twice over the past 12 years.

How much should I expect to pay these days? Where do you guys get yours? I found a few online and they seem to be about 600ish in price so far. Found one on ebay. Found one at a place called treasurecoastmiata.com. Does that seem right, pricewise?

Are there any 6 speed years that are better than others? I heard something about the MSM 6 speeds being shot peened, but that's it. Also, are there any quirks between the different years that would make them not bolt up to my engine/chassis?

With the 4.1 ratio rear, are going to be any significant gearing issues?

Is this a worthwhile upgrade or is it a waste of money? I see some of the guys (making a bunch more tq than me) have broken 6 speeds, but are they the exception rather than the rule?

600 is the low end of the standard market. You can pay less if you look hard, but 600-900 is the range.

The 01.5-05 boxes had better shifters, the MSMs had the best shifters and also cost the most (MSM tax). The MSM box supposedly had shotpeened gears, but it doesn't seem to improve the strength significantly. They're all dimensionally identical and bolt up the same way, but the shifter did change mid-year in '01 IIRC.

I ran 4.10s with mine for a while and didn't hate it. 3.90s are better, 3.63s are better yet.

If you break 5-speeds, it's worth upgrading.

^ the truth is spoken here.

upgrading to 6sp is a necessity, not a luxury.
track guys do it for better gearing, and street guys do it to hold more torque.
IMHO if I was only breaking 1 5 speed in 12 years I'd probably stick to a 5 sp

If you change to a 6 speed you are less likely to live up to your forum username.

Just paid a premium on a msm box with 55k on it.... $1300 from parts group. Just hope i don't kill it during the first track session one track build is compete.

To keep it alive:

Run a stock cast iron 1.8L flywheel (reduce peak torque spikes, reduce peak loading, increase fatigue life)
Organic disk sprung clutch (example: ACT Extreme)
Run good oil in the trans (Amsoil, Ford Motorcraft)
Install an oil cooler on the transmission (not easy, but trans coolers are done on high powered track cars for reliability outside of miataland)
Don't wheel hop/clutch dump it.

To the OP, I've bought 2 from treasure coast miata, so far Wesley has been great (I've bought a ton of stuff from him though).

I've been making over 260tq to the wheels and only ever broke a 5sp transmission with wheel hop on my torsen. Crappy pavement (asphalt patches w/ loose material) broke both wheels free until *BANG* 3rd gear was dead. It was rock solid stable with no issues up until then though.

Six speed availability and price and strength, generally?
 

You forgot "shield transmission from exhaust heat".

So is the 949 twin (organic) disc just asking for trouble?

I'm still gonna use mine regardless. I will be cooling both trans and diff, wrap exhaust or mad shielding, I only use Amsoil, and can't wait to try it out!
The set goal is 450rwhp on E85 - curious what torque numbers will be as i have a one off set of cams from TSE - more lift and duration.