Bad rear end

[Clapped1453]

I got a 14 5.3 double cab 4x4 and most the time at speeds from 25 to 45 the truck will shake and vibrate I am thinking it may just need a rear end fluid change but I don’t know any ideas?

[StinkyCheese]

Have you had the tires balanced?  Depending on mileage it might need diff fluid change regardless, but I don't see bad fluid making the truck shake at speeds.