I know I'm digging up an old thread, but my 97 T-100 has done the exact same thing since I bought it 3 years ago. No vibration until right at 60 mph... sometimes worse, somtimes better, but always a slight vibration. I replaced the BIG-O tires with REVOs a while ago, and had COSTCO use a Haweka adapter and all. The vibration is still there. I think there is something off with some of the T-100s and finding the source of the problem has been an enigma. Oh yeah, new idler arm and steering dampner a few years ago. If anyone figures it out, please let me know.

Thanks,

Vern