The Ascona/Manta 400 uses the Commodore style axle which has a physically larger diff that won't fit in a GT etc housing, but the axle shaft spline count and diameter is the same as on the GT etc shafts. The standard 400 gear ratio is 3,18:1 and is very rare with only a few hundred cars made.Seller wasn't to much help. Haha
As far as we know it fits any of the standard ratios fitted to the RA18 axle - so the axle MUST be an RA18, please see:
The video has no sound and is just the rebuilding of an Ascona rear end... with spider gears. Is there a standard gear ratio for Ascona's?
CIH engined Manta/Ascona B's could be had with several ratios depending of the engine. 3.44:1 3,67:1 3,89:1 4,11:1 and 4,30:1