Engine Noise on 2551 with 6.0 Ford Diesel

Just purchased a 2006 PC 2551 with a 6.0L diesel engine.  The engine noise level in the cab is almost unbearable and I'm deaf.  My lady friend isn't and can't stand being in for too long.  Imagine how it is for the cats. 
I have reduced the noise level by adding Dynamat to all surfaces within the cab and also in the engine compartment applied noise dampening material.  The engine noise is slightly reduced but we are wanting to know if anyone has any other ideas or has also experience this noise problem.

The cats have noticed what a rough ride it is aft.  This is my third motor home and it's the best looking of all...now if only I can solve these problems.

Ernie Brooks

I can't say I have a diesel, I assume it starts noisy and quietens down (though not enough) as it warms up. That's what I'd expect and that even applies to my 6.8 petrol engine to some extent. I'm somewhat surprised that dynamat hasn't fixed things. Are you confident that you are closing the doghouse properly? Check the air filter is new and isn't overly restricting airflow. Also maybe check your manifolds are not blowing or heat shields rattling.
I can tell you my experience of a rough ride. It certainly seemed that I could feel every bump in the road but I recently replaced all my tires with fresh michelins and that made a huge difference. Seems the old tires which were certainly rotting had lost a lot a flexibility too. The change made a huge difference. I also had an alignment and the castor/camber was reset. That improved forward stability significantly. The mech told me that the added weight of the RV fit throws out the settings of the the cutaway.
I would love my cats to ride with me but they are not the least inclined, except one that has already P-diddied in the passenger foot well. She has no shame.
Good luck with the 2551, I would really love to have the twin bed one... my perfect camper!

Your complaint of the diesel being noisey, is mentioned by many across all Ford E450 diesels, regardless of RV brand.  Like the previous reply mentioned, be sure your engine cover is seated properly with the rubber gaskets not being folded or distorted.  It is very easy to install it in such a way that causes extra noise and heat.

A 2551 is also going to provide a fairly rough ride because the 2551 RV conversion is on the lighter side of the E450 spectrum of motor homes.  The longer models are heavier.  The closer you are to the max weight rating of the chassis, the softer your ride will be.  Again, this rule applies with any brand motor home.  Not just Phoenix Cruisers.

Our 2350 model is built on a 2007 E350 chassis.  Loaded up with water, gear, food and two people, our 2350 weighs about 1200 pounds less than the max rating of 11,500.  The ride is only a little rougher than ideal.