i am trying to establish what diff my 91 vr4 rs has the label is pretty hard to read but it has a C1Y then underneath it has 3.909 but cannot read the above. is it a viscous or another type of lsd, ive searched high and low but cannot find much im buying an evo 3 rs gearbox and transfer case and to my understanding it will work fine with my 3.909 rear lsd, this car is jdm has 4 bolt rear etc will the axles i get with it work or will i have to put an evo3 diff inside my diff housing to use the axles, will update when i fit it up but a heads up now would be good damn evo3 rs stuff is pricey but my gearbox is stuffed.

Who told you it will work fine? I'm not saying they are wrong, they might be right, but alarm bells are ringing and I'm racking my brains as to why. I seem to recall that the EVO III DOES have a 3.909 final ratio but if I recall the EVO III transfer case is a DIFFERENT ratio to the VR4 and DSM ones. I also thought the transfer case used by the E38A RS was the same as that of standard VR4s.

I know if you use an EVO III rear diff you are supposed to use the complete EVO III drivetrain, i.e. box, transfer case and rear diff. I am ot sure what throwing the VR4 rear diff into the mix would do. I would probably err on the side of caution and put the EVO III LSD in the E38A diff housing but the differences might be so minimal as to make it unnecessary.

I think people have run full EVO III boxes with standard transfer cases and 3.909 rears but I'd still research this a bit more.

Evo1-3 share the same 3.909 ratio as the 89.10 onwards RS and 90.07 onwards Evolution E39A Galant VR-4s.

The Evo3 transfer case does indeed have a different ratio and needs to be matched to an Evo3 gearbox, however if you use an Evo3 box and transfer case together it's fine on the rear 3.909 ratio. The difference is in the final drive of the gearbox to the front differential.

The Evolution spec (and possibly 89.10 onwards non-Evolution RS) transfer cases have the iron head 23 spline type which is shared with the CD5A Lancer GSR 1.8 4WD (ie have the exact same part number), however it is common knowledge you can use the Lancer Evo1/2, 7G VR-4 and N23W RVR transfer case in place so long as it's from a 5M/T transmission. The earlier non-Evolution VR-4s and the pre 89.10 RS uses the alloy head 22 spline transfer case.

Quoting BENE38A:
i am trying to establish what diff my 91 vr4 rs has the label is pretty hard to read but it has a C1Y then underneath it has 3.909 but cannot read the above. is it a viscous or another type of lsd, ive searched high and low but cannot find much im buying an evo 3 rs gearbox and transfer case and to my understanding it will work fine with my 3.909 rear lsd, this car is jdm has 4 bolt rear etc will the axles i get with it work or will i have to put an evo3 diff inside my diff housing to use the axles, will update when i fit it up but a heads up now would be good damn evo3 rs stuff is pricey but my gearbox is stuffed.



Providing your rear diff is original and hasn't been swapped out you will have a 1-way plate type LSD rather than the viscous LSD of the 4-bolt E39A's. It is the same center as the Lancer Evo1, the Evo2 onwards went to a 1.5 way plate LSD. I believe the 1.5 way LSD centers can be swapped in no problems. If you had a viscous LSD originally then that's when you would need to swap rear axles or the axle cups at least.

In short the Evo3 RS box and transfer case will work fine in your car - you may have the speedo over-reading though as the Evo3 uses 205/60 R15 tyres stock and the VR-4 used 195/60 R15 tyres, unless the difference in speedo drive output is taken up by the dash cluster alone.

well thats good because i brought the setup there are so many you can do and cant do's on the internet its mind blowing i cant even establish a good gear oil to use one says this the other that, cheers fuel

What would this forum do with out Fuel. /ubbthreads/images/graemlins/worthy.gif

Run out of gas and die on the side of the road. /ubbthreads/images/graemlins/rofl.gif

I'm saving this so I don't get confused again. Thanks for putting this all straight Phil.