JD 420 shaking

[bobag]

While mowing today, my 420 lawn tractor started shaking. I thought it might be mower deck related so disengaged it. Tractor continued to shake. Then thought it might be because of a bad spark plug. Changed them and the engine starts better now but it still has the shake. Suggestions on what to try or look for are appreciated.

 

[Acehardly]

You may want to check your driveshaft u-joints. when they start to go, the tractor will shake while running.
Tony