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A question we’re regularly asked at Limited-Slip is:
“what LSDs do we recommend to fit a Lancer Evolution”
First, we need answers to some questions:
Here are the differences and why they are important:
Evo4-6/TM cars have a ViscousCouplingUnit (VCU) controlling the centre diff (the VCU is in the transfer and controls the centre diff. (it’s a regular open diff) which is located in the gearbox).
TM Editions are slightly different, as some had bigger bearings in their transfer casings, similar to Evo7’s)
The OE front diff. is either an open diff. or a Helical Gear Diff (torsen/worm drive).
The OE rear diff. is a plated LSD on the RS, or the ActiveYawControl diff. on the GSR.
Evo 7-10 cars have an ActiveCentreDiff. in the transfer, controlling the gearbox’s centre diff., in place of the VCU.
The front and rear diffs are basically same options as the E4-6, although the AYC diff. did evolve into “Super AYC”, which is a more durable unit and varying sizes of bearings have been used in different cars over the years..
A) Road/track days or serious competition?
B) If competition, is it tarmac (smooth or rough) or gravel?
C) Or just outright drag racing (straight line, constant need for traction)
A) Standard (300bhp)
B) Tuned (350~400bhp)
C) Seriously modified (450+bhp)
It is not easy to come up with a compromise that caters for all surfaces.
Bear in mind some basic suggestions:
For tarmac, especially smooth stage/circuit, it is an ideal starting point to have strong/tight diffs at the front and the rear, along with a softer centre diff. setting.
For gravel/mixed loose surfaces, you should aim for a tighter/stronger centre diff. whilst still using a strong rear diff., but the front diff. can be adjusted to suit the driver’s preferred style. The stronger centre diff. will make the car understeer, and that is the main reason it is not ideal for tarmac.
Evo.4-6/TM, which has OE Viscous Centre Differential (Viscous Coupling Unit – “VCU”) we suggest:
For gravel we would recommend the KAAZ diffs. Front, Centre and Rear. The KAAZ front unit is a big strong unit. However, once fitted it leaves no space in the transfer for the VCU (it comes with replacement housing). That would leave the car with an Open centre diff, with no centre diff control, so KAAZ produce a Centre LSD to install in the gearbox, to replace the OE open diff.
The KAAZ units are mechanical friction clutch plate type LSDs, with belleville spring washers (also known as cone springs) for initial preload.
All 3 x diffs., Front, Centre and Rear, can be adjusted, but it requires removal of the diff(s) from the car and dismantling, sometimes the purchase and fitment of alternative parts (different preload, different ramp angles, and different friction levels are possible, some plates can be offset to reduce effect). This is probably not necessary at the rear, so start your fine tuning at the Front and Centre.
The above KAAZ units cannot be used in Group N, as they are not homologated. For FIA Group N you should use the Ralliart front LSDs, with a standard size VCU (which can be rebuilt) at the centre, and a standard or Ralliart rear diff (E8 =RA534828K1).
Cusco also offer a variety of rear LSDs which offer many set-ups for discerning drivers.
For tarmac, the KAAZ centre diff. would need adjusting, to allow a softer setting. Really that is better achieved with a VCU, so we recommend not to use the KAAZ front diff. (as it will not fit with a VCU). We recommend, therefore, the Cusco front diff., with their tarmac setting of Viscous Unit (50Nm – can be rebuilt to 200Nm)– these come as a set, LSD+VCU. They are available in RS Type, using small coil springs for initial preload, or MZ Type, using Belleville Spring Washers (Cone Springs) for initial preload.
If you need to comply with FIA Group N, it would again be the Ralliart Front LSD, with a VCU (set to a softer tarmac setting).