I bought a jdm FD motor and trans and it came with an OS giken twin plate and a close ratio gear set.
If you thought the jdm gearbox was short already, try cruising on the highway at 3500rpm

 

^ Do you have a short ratio diff? According to the chart, oem 5th is .8 and OS is .82, not that radical a difference?

How do you find taking off in 1st gear? Is it ok or is it a pig?

edit; what speed are you doing at 3500? so i can do a calculation and compare.

 

Ok, thanks for the info.

 

I should get my car back in the next couple of weeks with os gearset and 4.77. I still have factory twins and with good diff center and suspension even with lighter flywheel i think it might only just turn the tyres through the top of 1st when cold. Short top will be a bit annoying but if I manage to twin charge it next year I will swap the 4.1 gears back in or maybe even the auto gears.

 

^ sounds good. Keep us updated. I'm still waiting for mine. Ordered mine through RHDJapan about a year ago. Was supposed to arrive mid year, then september, now they have pushed it back till feb. I'm a bit worried about it.

 

Maybe talk to Marcus, he buys batches of them in. I got lucky, Ric usually keeps a set on the shelf, i was actually going to wait and try grafting a corvette box/diff assembly into it when i was settled into my cousin's place in Melbourne with shed/hoist/welding bay but it developed an oil leak from the box and i cracked the ***** and decided to stay bolt in. Marcus has sold a heap of diff rebuilds to guys with OS gears with the cusco lsd, solid pinion spacer and 3.9 auto gears and recons they love it.

having bolt in multiplate clutch options with standard gear is nice, I would have had to remake the tunnel, get half shafts, make a torque tube etc. Rear bias weight distribution would have been good for traffic light battles or the strip thpugh.

 

Pretty happy on first impressions.

Is a bit noisier than standard box but I have a hard mounted gearbox brace, will swap it out for rubber isolated one in time.

the new sycros are good, should keep improving for a while too. Still no Supra 6 speed getrag though.


the ratio splits are excellent for power down. I have the 4.77 gears with stock 255/35 R17 s8 fd rear end works well. Revs more at cruise but ratios are better for performance.


I wouldn't have thought coilovers and the diff would improve power down as much as they did either, really happy with how it drives.

 

Good to hear youv'e got it all happening and it works well. I hope mine eventually comes in sometime during my lifetime! Im really looking forward to having a long 1st gear that i can actually use and all the flexibility of the close ratios in between.
Just out of curiosity so i can compare - what rpm are you pulling in top gear at 100kmh and how are you finding 1st gear in general?

 

With the shorter diff it will be getting close to 4000rpm at 120. I have a lighter flywheel and ceramic clutch to get used to still but the taller first is a better gear. I'm hoping when I go Single/twin charged on WI I will have heaps more torque everywhere so may swap the factory diff gears back in if cruise annoys me. I don't think it will be an issue if not freeway driving a lot.

I'm guessing your rolling radius on the older car will be a bit smaller and lighter chassis so 1st with standard or close to standard gears should be good. 5th itself is only 3% shorter so probably won't bother you cruising.

 

Well thats good 1st gear isnt a pig. Sounds like your final gearing is a touch shorter than mine with 225/45/15 and 4.1 . Cant wait for progress on your fancy twin charge setup!

 

Why wouldn’t you just get the Par-Engineering gearset which includes WPC treatment and free custom gear ratios with an 8 - 12 week built to order lead time?

 

All ears for feedback on PAR. Straight cut/dog engagement is mega noisy /not real practical in a street car though, if you go syncro /heli cut not a lot of difference and if you option 5th you end up more expensive than OSG. Heard about several PAR and PPG fails in the past but it is always hard to tell what is going on, factory cases will only ever deal with so much too.

If you knew you were unlikely to get out of 4th on track and had short diff gears the taller 5th of the PAR is probably desirable. I wanted something immediately and Ric had it on the shelf.

I'm very happy with this box so that is good enough for me.

 

I forgot to mention free helical gear option. You have no excuses, sorry ...

 

Well if you had of mentioned them earlier..... Pretty expensive though.

 

 

800rwhp/550tq on par

 

Stock case?

 

About $2000 USD for 5 speed giken.

 

If it’s suitable for your needs then sure. I don’t think the engineering and material selections are quite on par with Par (hehe) but if you don’t need that level and don’t mind waiting until whenever then no need to go there. It sounds like OSG is a good set, but you get a lot of flexibility, WPC treatment, gear options, and a real build to order completion date on the PAR that provide a bestoke product for a reasonable price.

 

Yeah the time factor is a concern. If i had have know they were this slow i would have looked at other options. But price was a big factor. I was not aware of the PAR stuff untill you mentioned it, but there are other options at that price point too, but seriously, if i wanted a stronger synchro, heli cut box at that price point, i would be looking at something other than a mazda box altogether.

 

If you are in a factory case race class it would definitely be a good option. I wanted to stay close to OEM if I could, If i ever break this one it will be a tremec 6 speed which will give me a genuine cruise gear and similar 1-5 ratios or chopping a corvette "its not a transaxle" or similar into the back for that kind of money.

I hope you don't have to wait too much longer Wankfactor. Welcome to my factory gearset if you manage to bust yours in the mean time.

 

Monsterbox, how many rotors and s it an even fire engine? A box should be able to take near twice the "average" torque from a 4 rotor as it will from a 2 rotor as it is generally the peak impulse that kills them. Big advantage of making a power figure with a 3 or 4 rotor is less clutch/box required compared to a 2 rotor.

 

Its due end of Jan now. Thanks for the offer Slides, but i will probably try and get hold of a complete 2nd hand box for backup in case that happens.

 

One of the cars that ran a PAR here, the mechanic ended up cutting a hole in the body to speed up "rectification" work on the shift mechanism that happened at virtually every session during each meeting. Ended up biting the bullet in frustration "putting" a Hollinger in the stock case eventually....where the case there just accommodated the input quill, which is about all it's good for. Reality is, stock cased gearsets are pretty much a joke if you're doing anything half-serious - track day warrior might just be ok, OS will eventually **** the bed too......but for other reasons.

 

The thing I forgot to mention though is the Par pricing is a single gearset built to order. So that one gearset is covering all the machining setup etc. I think if a group of people offered a multi-gearset order that the price will drop more than you might think ...