Diesel Engines/Chassis - Preferences and Why?

In the 36 to 42 foot range you need a diesel and they will all have a 6 speed Allison transmission...all very good. Most will have a Cummings engine as Cat gave up on meeting pollution requirements in 2010 after lots of problems, especially in the larger engines.

For extended use in retirement you need plenty of CCC, cargo caring capacity for all of your stuff. 40 foot rigs after 2003 (they started gaining weight) can have very little CCC unless it has a tag axle which improves the handling dramatically and gives you 9000 lbs of CCC instead of 1000.

I made the mistake of starting with a 36 foot rig because that was supposedly the biggest for public campgrounds and as you can see in my signature I found that not to be true so I now say buy more motorhome than you think you need, one time...Not like me.

When I upgrading recently (sold my Dynasty to my son) I went back with much the same rig on a Monaco 10 airbag suspension...RR10S. Prevost, Newell, Foretravel...$$$$$ all use a 10 airbags suspension/chassis for the great handling with plenty of CCC.

Most rigs up to 42' will have the ISL 400/425 1200ftlbs torque...the max for the Allison 3000 tranny. Cummins had a wrist pin problem BETWEEN OCTOBER 17, 2005, AND APRIL 18, 2006, WITH ENGINE SERIAL NUMBER RANGE FROM 46543077 TO 46603939. I recently talked to a owner of one that failed (put a hole through the block) at 45,000 miles and put it out of service for years and with legal help Cummins finally gave him an engine for $15,000.

The reliability, fit and finish, and overall quality of my 04 Dynasty was very good based on the 14 years I owned it...so yes, I'm biased towards the big Monaco/Beaver/Safari/Holiday Rambler which were all built on the same assembly line after 2004.

Cummins and Freightliner have the biggest service networks.

This is really a Ford vs. Checy topic. You'll likely get answers from people who like their setup. Having said that I think the 3126 CAT / Allison 3000 combo in my Sahara is great!!! :)

Bottom line is if you're buying new, there are few choices anyway. You'll probably end up with a Cummins/Allsion combination and probably a Freightliner chassis. Most diesels are turbo charged as well.

CAT doesn't make an over-the-road engine, although if you get a motor home with a CAT engine, there are plenty of CAT service locations that will service your engine even though their main business is heavy equipment.

Study up on the switch-over years from no emissions controls to DEF. 2008-2010 were the schizophrenic years where nothing seemed to work right.

There are also certain years and model of Cummins engines that had issues with various components. I might suggest joing the Diesel RV Club chapter of FMCA and read the various posts in the forums.

The biggest advantage of a diesel is that the engine and all its noise is in the back and you and the DW can carry on a conversation without yelling.

Horsepower is only important to you if you're climbing a lot of hills and the only difference there is what speed you drop to by time you get to the top. If you want to be a big dog and pass all the peons on the pull up the grapevine, get 500 hp and pay for the extra fuel it burns.