Re: Rear gear ratio

Posted by Fred Puhn On 2011/4/6 11:07:48

The driveline alignment concerns the angle of the 2 u-joints. To prevent driveline vibration the angle of each u-joint must be identical. A small tolerance is OK (say 1 degree) to account for measuring errors and suspension movement. If the engine crankshaft is perpendicular to the rear axle (viewed from the top) then the u-joint angle is measured in a vertical plane. Do not assume the crankshaft is parallel to the rear axle pinion shaft. On some cars the rear of the crankshaft is lower than the front to enable the drive shaft to sit lower in the car. That angle on the front u-joint is compensated for by tilting the rear axle housing to obtain equal angles on both u-joints. On many cars this rear axle tilt is accomplished by a locating pin welded to the axle housing. Be aware of these engineering requirements when swapping engines, drive shafts, and axle housings.