Bump, to get over the slew of live ads today.

Thoughts on previous statements please :)

Thicker casing might be the only thing you can actually see without opening up the gearbox. It is a more durable transmission than the aisin gearbox, at least from personal opinion and there are others who have said the same. Durability is something people would prefer over the aisin. My S1 tranny gave out on its own without any abuse at 90k miles.

The gear ratio is also lower than the s1 which improves acceleration.

I'm not sure where you're getting that the it would be slower with the series 1 differential? It hasn't affected my ride quality or acceleration, all I know is I that for sure my car is faster than before, but I also have other mods.

I believe I am using the S2 throwout bearing, although a mazda dealer were the ones who ordered it, so I'm not exactly sure which one they ordered to be honest. But it should be the s2 throwout bearing.

Overall yes the S2 slightly weighs more than the S1, other than being a pain in the ass when I had to pick up the transmission, (I picked both of them up by myself for transportation) it's not like it weighs the car down by much. It is a better transmission than the S1, I do think the aisin gearbox was much smoother in the way it shifted than the S2, but it's nice to know that I have a better gear ratio and more durable tranny. 3rd gear seems to be the gear that typically goes bad for the aisin box.

I found a good read about S2 transmission internal sturdiest comparison attached below.

https://www.rx8club.com/series-ii-te...ussion-135710/
Reference post 16

So how much slower would an S1 with S2 trans be given the smaller final OE gear vs a stock S1
And if that's the case nd you are not tracking your car hence don't need the beefier trans out of a S2. Why do so many claim it's the best for daily driving as well? Doesn't make sense to make your car heavier and slower.

I use my RX-8 for track days and 3rd gear lets me go to 100 instead of 85. I don't consider that a drawback. ;-)

The couple pounds heavier isn't much of a drawback for the improvement in reliability. Before I did the swap I asked someone who manages an MX-5 Cup team (newer MX-5 uses the S2 trans) if I should replace with a S1 or S2 trans and she said hands down get the S2 trans.

Figured I would through this here.

S1 Trans Gear; 3.76, 2.269, 1.65, 1.187, 1, .843
S1 Diff; 4.44
S2 Trans Gear; 3.815, 2.26, 1.64, 1.177, 1, .832
S2 Diff 4.77

S1 Dif S1 trans; 16.6944, 10.07436, 7.326, 5.27028, 4.44, 3.74292
S1 Diff S2 Trans; 16.9386, 10.7802. 7.2816, 5.22588, 4.44, 3.69408
S2 Diff S1 Trans; 17.9352, 10.82313, 7.8705, 5.66199, 4.77, 4.02111
S2 Diff S2 Trans; 18.19755, 10.7802, 7.8228, 5.61429, 4.77, 3.96864

I don't know enough about gearing to provide a conclusion so please those with the appropriate knowledge feel free to share some insight on what to expect between the above.

Little reasearch and a little math later and I have some results

S1 Dif S1 trans; 16.6944, 10.07436, 7.326, 5.27028, 4.44, 3.74292
S1 Diff S2 Trans; 16.9386, 10.7802. 7.2816, 5.22588, 4.44, 3.69408
S2 Diff S1 Trans; 17.9352, 10.82313, 7.8705, 5.66199, 4.77, 4.02111
S2 Diff S2 Trans; 18.19755, 10.7802, 7.8228, 5.61429, 4.77, 3.96864

Top Speed@8500
S1 Dif S1 trans; 39, 65, 89, 124, 147, 175
S1 Diff S2 Trans; 39, 61, 90, 125, 147, 177
S2 Diff S1 Trans; 37, 61, 83, 116, 137, 163
S2 Diff S2 Trans; 36, 61, 84 ,117, 137, 165

Synapsis

S2 setup will provide better acceleration with a lower top speed.
S1 Setup will achieve slower acceleration but a higher top speed

It seems the best setup would actually be a S1 Trans and S2 diff, but considering the S1 trans is garbage compared to the S2 It seems that and S1 diff w/ a S2 Trans is the best all around setup, wish first gear had a little more output torque though.

Side note, if you are looking to enter the 200MPH club it is theoretically possible with a 3.9 diff(Mazmart sells) using either an S1 or S2 trans.

The good thing though is that if you're going to put a S2 trans in a S1, you're not losing on acceleration if you still have the S1 diff.

According to your numbers it's still better than the S1 setup, right?

First and second gear have faster acceleration only

Not bad though, good job on the info btw! This should clear up the misinformation... :)

[QUOTE=Carbon8;4479070]
S1 Trans Gear; 3.76, 2.269, 1.65, 1.187, 1, .843
S1 Diff; 4.44
S2 Trans Gear; 3.815, 2.26, 1.64, 1.177, 1, .832
S2 Diff 4.77

S1 Dif S1 trans; 16.6944, 10.07436, 7.326, 5.27028, 4.44, 3.74292
S1 Diff S2 Trans; 16.9386, 10.7802. 7.2816, 5.22588, 4.44, 3.69408
S2 Diff S1 Trans; 17.9352, 10.82313, 7.8705, 5.66199, 4.77, 4.02111
S2 Diff S2 Trans; 18.19755, 10.7802, 7.8228, 5.61429, 4.77, 3.96864

Wouldn't the S1 Diff with S2 Trans have a combined second gear ratio of 10.0344?
People are saying that S2 trans with S1 diff would provide better acceleration in first and second gear. The way I'm seeing it, the S2 only has a bigger first gear, so when paired with an S1 diff it will only accelerate better in first gear. (I'm not arguing for or against it, I'm just trying to solve this whole acceleration question.)

My bad on the calculation it is indeed 10.0344.

The other statement is false, it is already concluded that an S2 trans S1 diff is slower than an S1 accelerating whoever is saying otherwise doesn't know what they are talking about.

Also keep in mind the S2 trans is heavier than the S1

Great... lol well, this should clear things up now...

Get a S2 diff or higher final gear if you want faster acceleration if you have a S2 tranny in a S1. Unless you're going for a higher top speed...

Oh and in case you were wondering, the S2 trans is only 9.2lbs heavier than the S1 trans.

S1
http://www.flickr.com/photos/9krpmrx8/12748016193/
S2
http://www.flickr.com/photos/9krpmrx8/12747891425/

Ok so as ive read there are pros and cons to either. Really it would be personal preference for daily driving. That being said, with the better acceleration and lighter weight of a s1 transmission but the cheaper quality would it be worth it to buy a rebuild kit for the s1 with better quality parts than OEM. Do you think doing that would let it take more abuse for occasional track driving?

Couldn't you at least have the courtesy of fixing your posts ...

Just curious if anyone running the S2 trans in an S1 is also using the S2 spacer plate (approx 3mm thick) between the engine & trans. I noticed when bolting up the S2 trans to my S1 engine that it took tightening up the mounting bolts to close up the last 3mm gap of clearance between the engine and trans. The gap wouldn't close up on its own (engine was out of the car in vertical position with me dropping the trans vertically down onto it). Haven't installed it yet and was wondering if I should buy and install that spacer plate.

Also, the last S1 trans I shipped weighed 78 lbs, previous one I shipped weighed 88 lbs boxed up, not sure how it is anywhere near the weight shown in those pics ....


.

I just installed mine yesterday along with the new clutch, new clutch slave, and the PPF from the R3 and it bolted up like normal. I will look again on the R3 but I don't recall it having a spacer. And that scale is accurate, I used a weight to check it and it was spot on with the 45lb weight. But I will try another scale to just to make sure.

No spacer on mine, in and out of the car twice now. Bolts up just fine.

All S2's with 6MT and AT has the flat spacer between bell housing and rear iron fitted from factory.

Do you have any pics of this? I have not jacked up the R3 to look yet but I pulled my trans off of a 2009 R3 with 9,000 miles on it that is in my driveway and I am pretty sure there is no spacer. Once the rain stops I will jack it up and take a look to see if it is on the engine.

I posted a blurry pic years ago here on my car...somewhere.

Even S2 Auto's have them..

Attachment 220516

Doesn't look like mine has the spacer.

Interesting they show a S1 shortblock in that pic lol

Ok so I think I understand the number crunching and I've seen the speed chart on page 2 with the diffrent speeds, and diff. Set ups .. I am all for dropping 10-15 mph for top speed if it gets me a large boost to acceleration ... I mean when are u Ganna take a turn going 175.anyway .... But just how much acceleration are you getting.. please correct me if I'm wrong but from my understanding it seems a s2 trans and diff. Combo. Would b best for acceleration right ??

The spacer slips on the back end of the S2 engine over the trans positioning dowels and trans just sandwichs it in place when bolted up. Without it there is an open spot into the bellhousing on the driver side that small rocks etc could get in there and possibly mess with the clutch assembly. I would recommend blocking it off with some high temp racer tape if you don't have the plate.