I would advise all IRS owners to inspect their car’s rear trailing arms for cracking, as a breakage here could ruin your whole day. During an examination of my car’s rear suspension about a year after the diff mounts were fixed I noticed 25+mm cracks in both trailing arms. These cracks were in the outermost web of metal connecting the mass of the arm to the cylindical section containing the hub mounting. This is viewed most easily with the car on a ramp, the web runs longditudinally with respect to the car, and is adjacent to the brake back-plate. Check carefully for cracks here. I replaced both arms with ones from a scrapped 4A.