I've been frustrated with how long the gears are in the S54 transmission since forever. Especially on a peaky engine like the Beams, 4-5k RPM is a pretty frustrating experience -- the NA miatas end up pulling on our racecar there!
As far as I know, no one makes a close-ratio gearset for the S54 (plus, I can't run one because the racing rulebook the car is built against explicitly forbids it), and no one makes a shorter final drive off the shelf. So, I got a small batch custom made. With a 4.85 ratio (stock is 4.176).
Because transaxles are so much fun, this doesn't just mean a ring and pinion, but a ring and a whole output shaft. And at that point, might as well fully rebuild a whole transmission.
OEM ring gear bottom, new one stacked up:
![Image]()
OEM output shaft left, new one right:
![Image]()
Before we put it back in a box, let's go a little extra, WPC coat the whole lot, and arrange on the bench to snap fancy pics:
![Image]()
New ring gear is slightly larger so... "some" modification required to make room.
![Image]()
Nothing we can't do carefully with a die grinder. But still, some care required. Most of the clearancing was on the bellhousing side, but a bit on the middle case was a good idea too.
![Image]()
Also, a little clearance near the oil passages for the bearings.
![Image]()
Lots and lots more time to clean all the shavings that got everywhere later. And it was my first time fully building a gearbox, so took my time. But in the end, all parts went where they're supposed to:
![Image]()
Get the cases together, chop off an old axle to make a diff preload "SST", and we're good to go:
![Image]()
It's an mr2 we're talking about. Swapping a transmission, might as well take the engine out for a bath and few other small things (like retorque the head):
![Image]()
The good: it works! Only one track test so far, but the gears are gearing and they're definitely shorter. So many shifts.
Compare that to the stock gears where you can basically do the whole track in 3rd (with a couple of 2nd gear switchbacks).
A little too early to draw conclusions, but there's the not-so-good too. It didn't make the car dramatically faster. At least on this track, will test on many others too. This was a pretty long project and we ended up improving the Beams power band quite a bit in the meantime. So, now the problem it was supposed to solve is much smaller. Oh well.
As far as I know, no one makes a close-ratio gearset for the S54 (plus, I can't run one because the racing rulebook the car is built against explicitly forbids it), and no one makes a shorter final drive off the shelf. So, I got a small batch custom made. With a 4.85 ratio (stock is 4.176).
Because transaxles are so much fun, this doesn't just mean a ring and pinion, but a ring and a whole output shaft. And at that point, might as well fully rebuild a whole transmission.
OEM ring gear bottom, new one stacked up:
OEM output shaft left, new one right:
Before we put it back in a box, let's go a little extra, WPC coat the whole lot, and arrange on the bench to snap fancy pics:
New ring gear is slightly larger so... "some" modification required to make room.
Nothing we can't do carefully with a die grinder. But still, some care required. Most of the clearancing was on the bellhousing side, but a bit on the middle case was a good idea too.
Also, a little clearance near the oil passages for the bearings.
Lots and lots more time to clean all the shavings that got everywhere later. And it was my first time fully building a gearbox, so took my time. But in the end, all parts went where they're supposed to:
Get the cases together, chop off an old axle to make a diff preload "SST", and we're good to go:
It's an mr2 we're talking about. Swapping a transmission, might as well take the engine out for a bath and few other small things (like retorque the head):
The good: it works! Only one track test so far, but the gears are gearing and they're definitely shorter. So many shifts.
Compare that to the stock gears where you can basically do the whole track in 3rd (with a couple of 2nd gear switchbacks).
A little too early to draw conclusions, but there's the not-so-good too. It didn't make the car dramatically faster. At least on this track, will test on many others too. This was a pretty long project and we ended up improving the Beams power band quite a bit in the meantime. So, now the problem it was supposed to solve is much smaller. Oh well.
