Here's a stock WRX 5mt:
This is a 5mt out of an '05 Legacy GT with the same ratios as the non-RA STi 5mt. This looks a little beefier in 1st and 2nd gears than the wrx and has a 4.11 final drive to put a little less strain on the drive and driven gears.Notice that the 3rd/4th gear hub on the driven gears has the worm gear cut in to drive a speedo sensor even though the LGT uses the ABS sensors for speed... This would suggest that these are infact identical to the non-RA STi gears. The first gear also has a dual cone synchro.
Below are the internals of the well known v6 STi RA 5mt. There seems to be some confusion as to whether the STi RA gears are really any stonger than '03+ (1mm wider than '02) gears. While the width is similar, the tooth root width is much wider on the RAs. This is the main characteristic that makes them able to handle a bit more than US wrx gears. Metalworking is possibly better on the RAs as well. Notice the difference between the drive gears on the left in the second picture. While being still a little shy of mythical PPG strength, these are looking a lot closer in size. Those who say the '03+ gears are just as strong as the RAs are obviously not paying much attention to the differences in the cogs.
Now let's look at a 5mt with PPG helical 1st/2nd (lighter color on the right half) and stock '03+ 3rd/4th/5th (left). Look at the difference in tooth root width! Wow!
Ok, now for a mid-90's Honda Civic 5 speed. Anybody wondering why a car with well under 120hp transmitted through only 2 drive wheels in the front is equipped with gears that are at least as beefy as our 5mt (mounted behind well over 220hp and driving all 4 wheels)? This might have something to do with the 5mt's orginal design based on a sub-100hp fwd car.
Here's another FWD application. You can find these connected to anything from mid 80s Volkswagon 1.8L and 2.0L 8v and 16v engines to the popular VW 1.8t engine producing about 180hp through 2 drive wheels up front. I've actually seen this box open, and these gears probably are even a bit more meaty than the ones in our 5mt, not to mention they have a noticably wider tooth root width (look at first gear: furthest down).
Next up. 1980s Toyota pickup. These boxes can be found behind millions of toyota 22r engines. I drive one at work that has well over a quarter of a million miles of union asshat railroad workers puposely driving it into the ground. Still shifts like a dream on the original trans. So that's about 110ish hp through 2 rear drive wheels with no weight over those drive wheels, and it still has way bigger gears than a 5mt. I think that reverse gear is about as big as a PPG straight cut 5mt second gear!
Alright. Let's look at some real transmissions:
It's not the best picture, but this is what a 6mt looks like inside. Those first and second gears (on the left side of the set) look particularly heavy. No wonder these are well known for their ability to take abuse. With this, you'd be worried about snapping axles and toasting clutches before the gears throw in th towel and let go.
Here's a stock gearset out of an m-22 Muncie 4 speed box bolted behind all sorts of chevy small and big block v-8s in the mid-60s through early 70s (rwd of course). I'd put these up against just about any other automobile gearbox, as they are BIG in person. My friends dad has these behind a built 327 in a '67 camaro producing around 380hp at the crank with probably as much torque at 1800rpm as a facotry STi produces at it's peak... It works beautifully, and did I mention that his Muncie has been in the car untouched since 1967 and has about 150k miles on it?
Here's a newer M5R2 variant of the venerable ford "top loader" found in supercharged ford t-birds. Try to break one of these. For a rwd platform at around 240hp, this sure makes our awd 5mt look very sadly short of suitable reinforcement and certainly not a great match to it's application.
Last, but possibly the best. Here's a T-56 6-speed box found behind many an american v-8, sometimes bolted to 400+ lb./ft. of torque. Those gears are soooo WIDE!
