Please fill out the following to ask a question. MAKE:Chev MODEL:Silverado K20 4x4 YEAR:1984 MILES:145000 ENGINE:7.4 DESCRIBE ISSUE....I'm trying to find the reason for my vibration at speeds of 55mph+. New Michelins and steel rims balanced/roadforced three times, rear driveshaft w/new spicer u-joints balanced, etc. Harmonic balancer appears fine and engine in smooth. Can/does the front driveshaft spin in 2H range that could cause the vibration very similar to a tire out of balance? The front driveshaft is original and has not been serviced other that grease. Very minimal play in the joints. I have the original auto hubs that require you to backup 10feet or so to make sure they unlock. thank you for your time to reply.