Growling noise and not changing speed after second

The vehicle listed above is an LT model. First, when I picked up the truck from a friend it was not moving due to rear end lock up; it has been sitting for many years. I had it towed to my place. A ask local mechanic and he advise me to replace the whole rear end assembly. I replace the rear end differential assembly (used) from Northwest Auto Parts Anchorage and after it was growling coming from the center and front of the vehicle. I spoke to many mechanics, and everyone pointed out my front axle. So, I replace both new and still the same issue. Then I replace the Transfer case rebuilt from Powertrain Products company and still the same issue. Please help!