Cat 426b vibrating violently at higher rpms

[Alexp08]

I was running my backhoe early and all was good, until I noticed it was shaking more than usual. So I shut it down and started it back up and all was good, I then put it into gear and hit the gas and it started again. The whole front end shakes as the Rpms go up. Any ideas?

 

[Alexp08]

Oh, 54xx hours, 1996

 

[Gary Fowler]

Could it be the harmonic balancer on front of crankshaft is loose?