Gear sets and final ration
 

Hi all,

Prob a silly question but does anyone know the 6 speed gearboxes enough to know what different gear sets there'd be available? I'm possibly looking at replacing my uk 6 speed gear sets (3.9 rear diff) and wonder if another set would fit, ie how specific on gear details do I need to be? Would an RA gear set still fit a uk due to final drive being different or is it just those gears decide what ratio you have and that's it?:wonder:

AFAIK....

There is the issue of drop gears to add to the diffs. some are 1:1 others are (?) 1.1:1 I guess to suit the JDM diffs front and rear. See TR column on the SPDA reference site.

The SPDA - Transmission Chart

JDM cars have lower 5th and 6th gear ratios, so will be quicker to accelerate.

HTH

dunx

I'm just about to have a Forester gearset fitted to my JDM 6 speeder. The diffs aren't affected.

Thanks guys...and there's me thinking the RA and the like of JDM's had lower 2nd, 3rds etc, didn't know it was just 5th and 6th.

Blimey, Forester gears straight into sti box...amazing what can be done.

Cheers for info.

Its the same casing, just different ratios

Jon if you dont mind me asking how much did the gears set you back?

Banny

Banny - YHPM

There is also a 1.081 to 1 drop gear ratio in the range :thumb:

Oh lord more complications....

LOL

dunx

Not kidding, another dumb question...how do you figure out these ratio differences 1.1, 1.0 and the other one? Counting the gear teeth on gear sets will tell you if its JDM or uk ratios, but dont understand this TR thing...:wonder:

DJ Jon, where did you source your forester gearset from? Are they the same strength as STi box? Might be interested in this route as I've seen the difference in ratios from 2nd and will be handy.

APi do them, speak to David - should be the same strength as any STI 6 speed box

Thanks, will do.

I have one new long ratio set left in stock, 2nd to 6th, 1st stays the same.

2nd) 2.235
3rd) 1.521
4th) 1.137
5th) 0.891
6th) 0.707

Where is that info from? I cannot see any reason why you'd need an odd ratio like 1.08:1 .

6 speed final drive choices are.

JDM 3.9 front 3.9 rear 1 :1 drops [ 30 teeth - 30 teeth ]

UK / Euro 3.9 front 3.545 rear 1.1:1 drops [ 30 teeth - 33 teeth ]

Multiply 3.545 by 1.1 too see why, if you don't get it . That is a device to cut down prop shaft speed which creates resonance in the cabin No other reason on earth why to do it.

There is no other option final drive ratio on any STi 6 speeds encountered so far.

1.08:1 must be a typo.

David APi

Cant seem to get an answer as to if these gear sets are same strength as sti? I'm sure sti gears case hardened....do you know m8y?

They are out of a Forester STI, so they will be the same strength as an impreza gearset. ring lateral or api

All gears, no matter which car, which model, across all manufacturers, are hardened to a minimum of 65 " Rockwell " which is a scale, much the same as the "Richter scale" for earthquakes. So there will be no difference in hardness between 1992 WRX gears and STi gears it is an industry standard.

What changes is the material compound that the gears are made of.

A certain popular UK based tranmission parts supplier, used to harden his gears like toasting a marshmellow on a barbeque. Naturally, at the time, they were a laughing stock in the transmission world. Nothing ever lasted beyond one rally or one race.

Dunno how they kept going, but they have.

Have no fear, your Forester gears are well up to the job.

David APi

Thanks all, just got decide which way to go now, gear sets or replacement box....Gear fitting expensive?

If Api, Z and Grade A are out of stock for DCCD gearboxes, anywhere else to get them from?

I watch ebay,
but I'm also considering a £1100 fixed 35:65 split centre diff. from Japanparts :eek:

dunx

Dunx, how come you've not gone for the DCCD's on ebay at alot less? I just dont know which way to turn with it at the moment, going gearsets and diff change is an expensive option.:wonder: