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Mar 2, 2007

R32 A-LSD or Active Limited Slip Differential

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The R32 version of the Nissan Skyline GT-R had an all wheel drive system called ATTESA-ETS. For the R33 the Vspec had ATTESA ETS Pro which included active lockup of the rear differential, or A-LSD. The R34 Vspec also got the active rear differential.

A-LSD light added to an R32 GT-R cluster.If you are going to go, go all the way
This picture is of the light that was added to the dash of this R32 GT-R. In this case, not only did the car have the light, but it also had an actual active differential. Along with the active differential, R34 ABS, and an R34 ATTESA control unit was installed.

R32 GT-R with A-LSD differential
On a normal car with a limited slip differential, some difference in speed between the wheels causes a lockup, that can be via a number of different methods.  A fully locked rear end, or a spool as it is often called, makes turning hard.  Both rear wheels try and turn at the same speed. Since they can't do that while turning, you often hear hopping, skipping, and jumping.  However in a straight line, you want the tires locked together if possible.

The A-LSD or active diff tries to be the best of both worlds. An open diff when you want it, and a locked differential when you want it.  On the street cars- aka production cars, the only real input that we see effecting lockup is the TPS sensor, or throttle.  Off throttle the rear diff is open.  On throttle, it locks up. More throttle more lockup. 

R34 A-LSD and ATTESA system hydraulic diagram

This is in no way necessary for 99.99% of the people in the world. This was done more of an exercise, to prove we could.  There are a few companies in Japan that have done it, but it requires a lot of parts, wiring information, and overall GT-R knowledge to make it work.  You don't need it, but if you have to have it, it is possible.  No I am not going to help you for free. Work it out on your own.

That black box is a yaw rate sensor, normally for Hicas. This isn't for Hicas.  The bulkhead fitting is for an Accusump
However on the R34 Super Taikyu car, the ATTESA system actually used the Yaw rate sensor, that was normally used as a Hicas input, as part of the feedback for the A-LSD.   The ATTESA ECU is special, the wiring to the Hicas ECU is special, the programming is special. That ATTESA ECU does not exist for normal people.  This isn't necessary to just install normal A-LSD, but NISMO did it for a reason.

R34 ATTESA Pump, and A-LSD control

ATTESA - The Nissan Skyline GT-R All Wheel Drive System
R34 GT-R ATTESA ETS-Pro Circuit Diagram and Component Location
How to Bleed the ATTESA System
GT-R, GTS4, FX35, R35 Transfer cases
Diagnosing common ATTESA faults

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