My 07 does not shimmy. Causes include improper air pressure (check all tires for correct inflation), improper balancing of the tires, or out of alignment.
I also recommend the Safe-T-Steer. Some form of steering stabilizer is a god send. Why GS does not offer this as OEM or an option is beyond me.
07 TM 40D;ISL 450 Cummins(upgraded). Very happy w/coach
Gnarly toad to scoot around.
Geocaching, hiking, fishing, National Parks, Civil War sites.