Gear sets and final ration
18 July 2009, 08:07 AM
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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?
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?
18 July 2009, 10:42 AM
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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
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
Last edited by dunx; 20 July 2009 at 05:38 PM.
18 July 2009, 11:51 AM
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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.
Blimey, Forester gears straight into sti box...amazing what can be done.
Cheers for info.
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18 July 2009, 10:30 PM
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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 quicker to accelerate.
HTH
dunx
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 quicker to accelerate.
HTH
dunx
20 July 2009, 06:37 PM
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09 August 2009, 09:56 AM
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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.
09 August 2009, 09:30 PM
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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
2nd) 2.235
3rd) 1.521
4th) 1.137
5th) 0.891
6th) 0.707
10 August 2009, 12:31 PM
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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
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
11 August 2009, 06:35 PM
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12 August 2009, 09:42 AM
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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
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
17 August 2009, 06:45 PM
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