Is it a shudder through the front or rear wheels?
If front, I'd check the bushes and track rod ends on all the steering parts ... and that the steering damper and it's bushes work too.
if rear I'd check rear prop donut (if it's a 300), then all prop UJ's, front and rear. I'd also check the A-frame bushes, both at the chassis end and at the axle end, use a long lever and try to force them apart. Also worth checking the trailing arm bushes and tightness of fittings. Almost any free play can cause issues and knocks.