[eschaider]

All IRS suspensions used fixed length upper and lower a-arms, Greg. In addition all half shafts are fixed length but usually with a sliding coupling like a drive shaft yolk on the output shaft of a transmission. That I am aware of no IRS has ever been manufactured, for production, with variable length a-arms or half shafts.

As the IRS suspension moves up and down through its range of motion the wheel spindle traces out a modified arc defined by the length and location of the upper and lower a-arms in conjunction with the design engineer's chosen pivot points on the spindle.

As the spindle moves through its range of motion there will be increases and decreases required in the length of the fixed length half shaft to make the connection between the side gears and the axle flange. The changes in required half shaft length are absorbed by either a splined coupling (like used on a drive shaft), usually near the center section, or travel built into the CV joints if the design uses CV joints.

Get yourself one of the free or cheap 3D Cad programs out there, draw up the basic geometry and move it through its range of motion. If you have difficulty visualizing spatial relationships in motion the 3D CAD software will help you see what is going on.


Ed