tuj

I seem to remember there was talk of a 5.5 final drive differential, but I couldn't find it with a search. Does anyone know what kind of options are available for getting a higher numerical final drive? I am looking for more acceleration, regardless of what rpms I end up at in 6th gear.

'ringmeister

i believe there is 5.2 sold by mazda competition parts that is used by the grand-am cup cars. very expensive, and that is too short IMHO for the street. the feed(?) 4.77 is a better choice and cheaper at around $700.

TeamRX8

iTrader: (25)

They dropped the 5.2 R&P price to around $1200, use to be almost $3500

tuj

The S2k diff swap gets you 4.777 I believe. I'm looking for something numerically taller than that. Is the Mazda comp unit just the gears, or does it include a whole new LSD?

Is anyone selling the 5.2 or is it just available from Mazda Comp?

mdw1000

Does anyone know if these differential swaps would make a big difference in 0 to 40 and/or 0 to 60 times on a 4 speed AT? If they do, seems like this might be a good option to get better low end acceleration without having to go to the expense, reliability issues, etc of FI, if you are not looking for enourmous gains.

tuj

I am not sure what ratio is on the AT, but a shorter final drive (higher numerically) will always increase your acceleration, at the cost of top speed, and higher revs in top gear. Remember, I'm perfectly willing to accept those trade-offs because I am considering making my RX-8 into a track-only toy. I would not go higher than 4.777 on a street car.

Now, in terms of 0-40 or 0-60, you might end up with an extra shift, which could slow those times down, but overall your acceleration will increase.

redcivic

Any info on the s2k swap?

mdw1000

tuj,

I got the optional LSD, so I'm guessing my final drive is the same as the MT.

Not really concerned with top speed. It is plenty fast for me on the public roads. I would like more low end grunt.

Has anyone done the 4.77 swap from FEED?

rotarygod

I personally feel that your cars already have too much rear end ratio in them and need to go down. Going up is really a waste of time unless you are in a certain racing class. If you just want more acceleration, this really isn't a very logical way to go about it. Forced induction would be the best choice.

mdw1000

^ Yeah, but FI is a lot more expensive and pretty much voids the engine warranty.

Not that I disagree - I'm really considering Petitt's SC. Just researching other options as well. If I can get a little more noticeable low end grunt for under 1k I might do that soon. Might still do the FI down the road.

I did see a review of this in the far east forum where the guy was raving about it.

And from what I've read today it sounds like the 4.77 is the choice for street applications. The 5. something isn't available unless you are involved with mazda motorsports.

mdw1000

rotarygod - I also meant to ask why you think this isn't such a good idea?

Fanman

higher ratios means that in the gears you are running at higher revs at the same approximate speed. i.e right now if you are cruising the freeway at say 3800 RPM already, you might be at 4500 rpm with the new gears. Using more gasoline, putting more wear & tear on the engine, buzzy, etc.

If they offered a higher ratio in the first 4 gears & lower ones in 5th & 6th this car would be about perfect.

mdw1000

^ but wouldn't you be putting more wear on the engine, etc with FI as well?

Fanman

Yes, but I was just talking about a regular RX8 and throwing a diff. on there. A turbo would put more wear and tear on the car. Unlike parts like an air intake, hi-flow cat, lightweight flywheel, etc that won't really affect driveability of the car or wear and tear too much.

PS : a upgraded diff. is not going to give you the acceleration like a FI'ed RX8.

swoope

iTrader: (5)

it is 4.3 for the 6 speed auto.. i think it is 4.1 for the 4 speed auto...

beers

tuj

Ideally someone should sell a new 6th gear that is way taller, and then lower the final drive. Maybe 5&6 (are they on the same shaft?). Then we could get the best of both worlds. I really don't know what Mazda was thinking when they did the ratios on this car....

So...is there any way for a normal person to get the 5.2 unit, or do I have to paint my car like the 787b? :-)

mdw1000

swoope,

Is that true if you get the optional LSD? or are you at the same as the MT then?

mdw1000

Yeah, I realize it is nothing like FI, more of a mod to give you some but not dramatic improvement. Guess I'm wondering if this would be good enough for me for now to help improve 0 to 30 and 0 to 40 times for merging into traffic from a side street, without going to the expense or risk of FI?

tuj

Um, the 0-30 times are already good. If that's where you want improvement, at stop->low speed acceleration, this isn't what you want.

peterisurhero

hey guys its "kinda" off topic but i was wondering, would it be better to go with a lower diff of the higher one if i am planning on going nitrous. which one would make it faster? i was thinkin the higher ratio diff but juss wanted to make sure and ask you guys.

TeamRX8

iTrader: (25)

Well there's typical RX8Club billion page long thread of drivel on the subject and nobody else has found an alternative other than the FD3 R&P's that I'm aware of (which BTW the FD3/SE3P LSDs are also cross-compatible). It's also worth more than just low end if it's being used with great success in GrandAm, but that is a pure racing scenario. The only other place I know of where you can buy a similar ratio is Astra Racing in Italy, but I'm pretty sure it costs more plus the customs and freight additions.



LOL, you come asking the question and now you're an expert on the subject

mdw1000

^ I'm sure the 0 to 30 times on the MT are quite good, but I'm talking about the AT.

tuj

Dude, I was asking about the availability of the a different ratio, not what it did. I don't know why you perpetually try to slam people.

That being said, I did not know that the FD diff was compatible, so thank you for sharing that.

TeamRX8

iTrader: (25)

my sister's baby girl might consider that a slam, but a man probably wouldn't have noticed ...


btw, that's a j/k too

tuj

Can you get to 30 in first gear? The MT can. What is your top speed in first and in second?