juddering

Car: Vauxhall Corsa 1.2L 2008 50000 miles My car shakes when I’m driving at 30-50 mph. I feel it mainly under my seat in 4th gear and low revs 5th gear, but my phone on my dash board also shakes, it’s a powerful rumble, but no difference to noise. It doesn’t shake more when I brake/steer. I...