hmmm you're a bit confusing when you wrote standard viscous centre with 2 spider, and open front diff? Might be better if you tell me the gearbox code on your Evo gearbox lol
Regardless whether you have viscous front LSD or not, you're going to get rid of the existing Evo front diff anyway and replace it with a Quaife. Just ensure that you use a normal open diff cv cup on the driver's side when you fit the Quaife in it.
Anyhow, changing from EVO 3 drivetrain to GSR 3.545 setup is the most involving because you cant keep the EVO 3 transfer case.
You will need to open your gearbox, remove the EVO 3 front diff with 63 tooth crownwheel and 15 tooth output pinion out of the box. Then fit a GSR 58 tooth front diff crownwheel to your Quaife ATB front diff and use a matching GSR 15 tooth output pinion. Evo 15 tooth output pinions are different to GSR 15 tooth output pinions. The teeth sizes are different and they stick out further on the GSR pinion. Dont let anybody else try to tell you any different. You cannot use an Evo ouput pinion with a GSR crownwheel or vice-vera... it wont work. Once you have the GSR parts fitted close your gearbox back up. In summary 58/15 = 3.867 front diff ratio.
Now, your EVO 3 transfer case is no good to you anymore as the EVO 3 transfer ratio is made to only suit the EVO 3 front diff ratio. ie. EVO 3 transfer ratio is 1.074. Now that you have a GSR front diff ratio in your gearbox, you will need a transfer case from a GSR, EVO 1 or EVO 2 which run 1.09 ratios. Out your way you should find an Evo 1 or 2 transfer case easy so use one of them. In summary 24/22 = 1.090 transfer ratio.
Rear diff is currently Evo 3.909 mech LSD. You will need to open the rear diff housing, remove the Evo crownwheel and pinion and replace it with a GSR 3.545 crownwheel and pinion, set the tooth alignment and backlash. Yes, the GSR crownwheel and pinion will fit inside the Evo housing using the Evo rear mech LSD. In summary 39/11 = 3.545
When doing the math now, you need to ensure the front diff ratio of 3.867 matches the ratio of the transfer case x the rear diff.
Threrefore transfer 1.090 x rear diff 3.545 = 3.864. That's the GSR front and rear diff ratios sorted.
You dont need to machine anything to make any of these items fit.
The centre diff is a completely different story. It will need to be opened and the housing machined. The cross-shaft in the centre diff will need to have the other 2 ends machined to suit another 2 spider gears, hence making a 4-spider centre. The extra 2 spider gears can be taken from another spare centre diff. Dont forget to use a total of 8 brass shims for the spider gears. The housing machining to accept the 2 additional spider gears will have to be done by a professional. Once done, you should end up with a cross-shaft that fits 4 spider gears which should fit nice and flush inside a newly machined housing.
There are a few companies out there than can supply additional parts for the centre diff like a hardened chromoly 4-spider cross-shaft and a machined top hat with a torrington bearing upgrade for the centre diff pinion to add even more strength and reliability to the centre diff. That's the way I went when building my own custom gearbox
A GSR gearbox when cruising at 100kmh in 5th gear according to the GPS, registers only 2850rpm on my AVCR
There's other combinations that can make 5th gear cruising even better with lower rpms, but 2850 is a nice sweet spot IMO when running a bigger turbo thats not producing positive pressure that low in the rev range.
Edited by EVO-00X, 02 March 2011 - 12:24 PM.
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