P71 wrote: kreb, The T-5 is actually a very weak. Even the Mustang 4.6's have Tremec's since the mid-90's (3550 or 3650 or something like that). 300 FtLbs is about the highest TQ a stock T-5 can handle. The T-56 is stronger and also has a huge overdrive in 6th (.5 to 1 as mentioned) which nets great fuel economy.
I would say the quote that the T5 is weak is a generalization, which I'll get to below. In V8 Mustangs, the T-5 was replaced by the T-45 in 1996 (with the swap to the modular engine). The T-45 was replaced with the T-3650 during the 2002 model run.
The Miata is a completely different application than a Mustang, so a T5 might be sufficient, depending on your power levels, along with what you'll be doing with the car. Some T5s seem to hold up well to abuse (high RPM launches on slicks, power shifting, etc.) whereas others break under the same conditions. The T56s are heavier than the T5s, are physically larger, and most claim they don't shift as smoothly as a T5 (I happen to agree). T5s can be upgraded for better durability, many outfits offer upgraded gear sets, etc. (G-Force, Astro Performance, etc.)
Most T5 issues in Mustangs seem to stem from drag racing, which may not be your primary activity in the Miata. Even so, launching at a high RPM on slicks in a 3200-3600 lb car is far different than auto-xing/road racing/daily driving a Miata.
DJ
