Figure 1 shows schematically a perfect aligned forward drive train. Note how the rear face of the engine block (A-A), the crankshaft flange (B-B), the forward face of the flywheel housing (C-), the rear face of the flywheel housing (E-E), the era bore of the flywheel (F-F), the mating surface for the clutch pressure plate (G-G), the pressure plate mating surface (H-H), the rear face of the clutch housing (J-J) and , finally, the forward face of the transmission (K-K) are all absolutely parallel, with their centerlines exactly on axis X-X. Read Flywheel Alignment Pt 3 for more on the subject