Anybody using 3.636:1 ring and pinion?

[CarCar]

I haven't had any luck finding a 3.9 R&P set for my 5sp '01 NB. Mazda discontinued the set and I am hesitant to pay a premium for a salvaged set I can't get supplier to warranty. I am currently running intercooled TDR MP62 with 7# flywheel and stage2+ clutch and freeflowinf exhaust. I have not put the 62.5 pulley and 550cc injectors yet but I will in near future to complete my power upgrade. I beleive I will be about 215 hp with tune then.
Currently where I am with the 4.3 R&P 1st is useless and cruising the interstate at speed my rpm are high around 4200 to 4500 killing fuel economy.
With standard gearing on a spreadsheet it appears I can cruise at 3450-3500rpm at 80 mph and have a useable 1st with the 3.6 R&P.
This is the R&P I am interested in http://miataroadster.com/mmd.html for $495 and $125 to install.
The other option I see is a close Quaife gear set with a tall 5th. $2800 for the set and $600 to have installed and another $300 to swap the Tranny in and out. I don't like this option.
The 4.1 R&P with standard gearing I don't feel is enough of a difference to make it my worth. Am I wrong with this assumption at my power. On the spreadsheet not much of a rpm drop at the 75 to 80 mph cruising nor much difference on 1st.

I use the car as daily and also enjoy track time with it. Is the 3.6 to tall and will it kill the fun factor at my power level? When the pitch is to "high powered" is that implied to only V8's and such?

I am not currently equiped with a Torsen and between deciding on a used one or a new OSGeiken clutch type if my open finally gives up. The Torsen I am uncomfortable with salvage parts and lacking of warranty especially for the prices I can find on '01-'05 around $1000. The OSGeiken is just expensive, $1400 but is warranted and is extremely smooth and forgiving I have been told.

If you have experience with the the OSGeiken could you share? I have found plenty of opinions about the Torsen and it seems to be the benchmark Miata diferential. I have never had an oportunity to drive either of these difs.

Thanks in advance for a helpful discussion I hope.

[trickyrix]

I think Gary (trackdog) and Shawn (Magma) are both running 3.63 gears.

[Radio-Active]

I have thought about it and I think Wags just put a set in.

[CobaltFire]

Magma is running a set for sure. I am seriously considering it myself; everyone who has them on a F/I Miata seems to love them.

[Nexus Flux]

I think Gary (trackdog) and Shawn (Magma) are both running 3.63 gears.

I'm pretty sure that's what Shawn has, and from what I have heard that is what Gary is going to. Shawn is an MSM and Gary is running a blower.

[SirHustlerEsq]

The 3.63 is too big for a 5-speed. I have a 3.63 on my 6-speed and it's great. The 3.90 is great on the 5-speed if you over 275whp on a dynojet...which I'm estimating from experience.

I'm making well into 300whp on the same 1st ratio as your 4.30 5-speed and first is not useless. You won't use it on the track of course, but it's not unusable on the street. You're not going to find many cars that can use 1st in a track unless you drop some serious coin.

[SirHustlerEsq]

Also, go with the clutch diff. My torsen lives a sad existence. It's inneffective and probaly weak.

[Miatamaniac92]

Also, go with the clutch diff. My torsen lives a sad existence. It's inneffective and probaly weak.

So trade for an RX7 clutch dif?

Chris

[SirHustlerEsq]

Yeah, that clutch diff is pretty good from what I hear. However, I'm going another route.

[Magma]

For once I agree with Trey, the 6 speed and 363 are great, and I think the 390 and 5 speed is the other good setup, but I have never tried it

[CarCar]

Why is the 3.6 and 5sp not a desirable combo? I can understand maybe in autocross where you probably rarely get out of 3 and want to leap quickly off the start. For track and daily cruising where there is plenty of time to wind up into the top of the tach the 3.6 looks, on paper at least with adequate HP, great for 3,4, and 5. On the spreadsheet it looks like you could stay in 1 longer and not have to shift to 2 before you exit the intesection around town.
As I said I am not having any success finding 3.9 R&P that aren't priced double a 4.1, 4.3, or 3.6. The 3.6 R&P just seems a better alternative to the easily available 4.1's. I have found a ton of 3.6 R&P from '79-'82 626's under $100 that are suposedly an easy direct fit into the Miata housing. The R&P with the electronic speedo drive from miataroadster is the way I would rather go but it is hard to disregard the 626 R&P availability and low cost.

[trickyrix]

Take a look at this and run some numbers... the ratios listed are overall numbers, so divide out 4th gear (or 5th in the 6-speed) back to 1:1 the recalculate the 6-speed with the 6-speed gear ratios. The 6-speed/3.63 overall numbers end up a tad shorter than the '99+ 5-speed/4.30 numbers, but you end up with a nicer O/D in 6th.

LINK

[SirHustlerEsq]

The 3.63 is harder to find than you think. If for some reason you've found a cache of them, I'm happy to buy a lot and sell them on the internet to all my e-friends.

You don't make enough power to use the 3.63 with a 5-speed, and you will be slower due to the wider ratios. I think the 4.10 on a 5-speed is the best gearing I've driven, but have the 6 in my car for strength reasons.

[CarCar]

The consensus seems to be the 5sp ratios are to wide to run a 3.636 on a track at my power level but may be fine for puttering around town and would do decent fuel economy on cruise but the fun factor may be a bit on the low end.

My 5 syncro is bad in my 5sp. Cost of repairing the tranny is more than replacing it. A $500 recycled 6sp with a 6 month gaurantee is headed my way. Also, I got real lucky today and found a entire rear axle assembly with a 3.90 Torsen for $500 at the same salvage yard. Man at the yard said it was not a locking but a LSD so he would let it go cheaper. Checked the VIN at a dealership and verified its a 3.90 Torsen LSD. This (3.90+6sp+Torsen) seems to be a very popular tried and true combo I will try for a few months. I still want to go 3.636 R&P in the near future but I ran out of the green.