It's an issue of perception, not reality. In 1964 I inherited my late grandfather's 58 Chevy DelRay coupe with a 235 and a 3 speed (SM-318) transmission, and a 3.70 rear end. It also had 14" tires, the first year Chevy used that size. I drove it 65-70 MPH routinely, and mid to high 80's was not impossible if I really wanted to push it. I attended college 150 miles from home, and it was not uncommon to make the trip home on weekends in 2 1/2 hours or less. That's an AVERAGE of just under 60 MPH, with several 30 MPH speed trap towns along the way. Your truck is capable of much higher speeds than you're apparently willing to drive it. Take the fan off and make a highway run, and I believe you'll figure out where most of the "engine" noise is coming from. Your speed is directly proportional to the position of your right foot. I can highly recommend the purchase of a pair of earplugs. They're a lot less expensive than ring and pinion gears.
Jerry
