Editing Differential FAQ (section)

==What diffs came in the R31?==
The R31 Skyline and Pintara came with either a BW75 or BW78 differential depending on year and model. It is reckoned those cars that came with factory LSD used the BW78 diff, along with the last 1990 built Series 3 examples. The two diff types are ostensibly the same, except for the crown-wheel/pinion mesh geometry. This change requires modification of the BW78 pinion, to make it fit the BW75 housing, but it works fine. All other parts are interchangeable between the two types. The 4.11 ratio diff fitted to the Pintara is a BW75, the BW78 wasn't manufactured with this ratio option.


There is no visible way to determine a BW75 from a BW78 externally, and even gear set part numbers are common for both types. Another consequence of the mesh helix change, is a slight shift in effective drive ratio.


The Skyline had a 28-spline, 4-pinion center.

The Pintara had a 25-spline, 2-pinion center.


The Skyline center is naturally therefore stronger than the Pintara center.


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2 pinion diff


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4 pinion diff