3.909 gear ratio installed, first impressions

I picked up from Bulletproof Automotive some Tracy Sports 3.909 gears. I arranged for Puddydad to install the cryoed 3.909s in my current '09 rearend and these are my first impressions.

I am running wide RA-1s in 275/40/17 and a light weight Comptech flywheel that makes driving with taller gears a little more difficult when starting. This is similar to the change I noted when going from 4.44s to 4.10s. Starting out on a hill requires a little more clutch slippage than I am used to.
With the 9500 redline first gear pulls to just shy of 50mph. It seems to accelerate just a quickly as before but with more authority. It holds to the ground slightly better and thus first seems to be more useable. This thing really gets going.

Second gear is a hoot and peaks out around 75mph. Third gear seems to pull just as quickly and yet ends up going 105mph third.

Fourth gear Rubber shorts time.

Fifth and sixth on the freeway are very civilized. I like cruising at 60mph turning 3050 rpm in 6th.

Overall impression is the car is more fun to drive with more speed in every gear.
Well worth the trade off with starting out difficulties.
For those that are curious, I don't check economy.
And yes, the differential has been polished.





Thanks to Puddydad for the timely and very talented install. The differential ended up quiet with no hint of whine.
Thanks to Ben at Bulletproof Automotive for sourcing the gears for me.
Thanks to Tony Fuchs for the quality install as always.
Thanks to Roger at CryoScience for cooling my parts.

nice, I might look into these for myself

what are the stat's on your car? I assume it is FI, but i the link to the dyno in your sig is bad.

I believe his car is Supercharged via Vortech and is putting down around 500hp+.

Sideways, are you currently using the AP1 or AP2 transmission?

I am currently running my four hundred horsepower tune. That is, 499.4 rwhp. I don't have a copy of the dyno.

This is a slightly different more agressive tune:


AP-1 tranny for the taller 1-4 gear ratios.

I'm considering running the 60 to 130 mph competition with the six speed guys in Texas.

Have you thought about doing the Texas Mile as well?

COOOOL!!! im glad you like these gears. im having these exact gears installed as well. Great review!! it must be nice to be able to use 1st gear lol

cost of gears?

http://www.bulletproofautomotive.com/catal...ail.php?ID=4241

^^^^^ theres no way i'd pay that much for gears. you've got to be kidding me

Don't worry, there is less expensive 3.90 gears available

Glad you are enjoying the new rear build Sideways, good luck with the car

i have a set of 3.9 gears that puddydad installed for me. Been going strong for about 8k miles! Puddydad did a great job

ben is the best go puddy dad

I can understand that response.


Puddydad should be able to source you some gears at a more reasonable cost.

That's nuts. I like how you call it your four hundred horse tune.

hoooly crap, I hope those aren't the gears he really "sourced" through Bulletproof. He knows himself that they are just mazda gears. Probably only a couple hundred bucks from the dealer.

I like everything I see here. Are you a 2.0L still? I assume so with being able to make power past 9,000RPM

Sideways thread is not about the gear set price or brand but, about the performance difference he has experienced with the 3.90 ratio. Please don’t cloud his thread over money spent for a set of gears, it was his choice

I did not source these gears for him, he supplied them to me for the job. The gear ratio is not cheap. Mazda is about $700 to $900. You can also go through Mazda Speed but, you must prove you race a Mazda to get the discount.


Back to topic

i clicked the link to see just how much they were. omg. i mean, i aint hatin, just, well, OMG.

sideways, glad they are working out, its so true, once you start making real power, taller is the TITS

Nice review. If I was turbo making 400-500hp, or making the kind of power you're making on the SC, I'll send my puddydiff back for this gear swap in a heart beat.

Well, lets put it to rest about the cost as I wouldn't, couldn't, and didn't pay the price listed at Bulletproof.

With the increased power lower gears are holding the S2000 back. Driving with these gears makes the car seem in another league, one with much faster cars.

Puddydad may need to obtain these in quantity when the word gets out.

My impression is 3.909 gears are the TITS.

Sideways, at what power level would you say the 3.9 ratio would be effective? Above 300? 400?

I would say when you reach the 280 to300 ft lbs range of torque you are ready to take advantage of the 3.909s.
Anybody putting out 350 or more ft lbs of torque would definately benefit. More torque would benefit from even taller gears. Possibly 3.63s or something in that range.

Hey Ben, refresh my memory, what ratio is available that is taller?

there is a 3.636 as you said available from mazdaspeed, I've seen some miatas using it.