Setting Pinion Angle
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An IRS, unlike a solid rear axle, has a fixed differential housing. It does not move when the suspension travels. So setting the pinion angle can be done on a drive on lift with the suspension loaded, on a two post lift or on jack stands with the suspension in full droop. It does not matter. |
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Lay the tip of the non-moveable portion of the angle finder on the rear face of the transmission tail shaft housing as shown above. Be sure the scale is locked in the angle finder so it cannot slide. |
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Match the scale to be parallel with the drive shaft, then lock the angle finder thumb screws to secure the angle setting. Read the angle and write it down to reference later. |
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| Now lay the tip of the non-moveable portion of the angle finder on the differential pinion flange face. Again, adjust the scale to be parallel with the drive shaft and lock the angle finder thumb screws to secure the angle setting. Take the angle reading and compare it to the reading that you recorded earlier for the front. The driveshaft angles must offset each other. EXAMPLE: If the front angle reading is +2 degrees (92 on the angle finder), then the rear pinion angle must read -2 degrees (88 degrees on the angle finder). Baseline for a Cobra IRS without purchasing the FR 1401 Delrin isolated rear diff lowering mount, is raising the front of the diff as high as you can get it without it hitting the subframe. This will not be perfect, but it will be an improved driveline angle compared to the way the car came from the factory. In order to perfectly off-set the driveline angle, you need to purchase the FT 1401 Delrin isolated rear diff lowering mount or the complete bushing kit FT 5001 which includes the FT 1401 lowering mount. The diff angle cannot be set until the subframe goes back in the chassis. No, the car does not have to be level doing it this way.  |