Ours on our 3400 was VERY noisy, at first. So, like most, I got in there and insulated/tightened/relocated lines and fittings. It helped a great deal. It also helps to have a "helper" turn the water on and off while you are under there so you can see and feel what is actually making the noise. I also went one step further, I bought the Shurflo "bladder" tank and attached it to the discharge side of the pump. The bladder tank is one you pre-charge to a certain air pressure. Like well systems, it gives you a bit of draw down capacity before the pump kicks on, and then the pump runs a bit longer charging it back up before it shuts off. Saves wear and tear on the pump, and it helped quiet it down too.
