Need some advice here! On my '48 3/4 ton, when going down the road @ around 55, she starts to vibrate & goes away around 65. I pulled the drive shaft & had it checked & had a 4 wheel shop balance the tires (new tires) & check the rims for balance. The king pins are new, I've added an open drive shaft & T5 trans (that I had rebuilt). The vibration is not felt through the steering wheel. I have the shims under the springs & the leafs I rebuilt . Any ideas would be appreciated.
