A few comments on Slowtrot's excellent post. (My experience goes back over 60 years from large gensets, 8D cat, over a dozen boat diesel engines, up to 375 hp, Farm tractors (4 on our farm) and many years ownership of RV's with diesels, plus a couple of light trucks. The very newest of the diesels are lighter due to higher RPM and lightweight materials. However, they are much more complex electrically (electronics). It used to be air and fuel---a diesel would run. Today, you have to have all of the electronics going, and a new part of the equation: UREA (DEF) which is injected in the exhaust to decrease nitrous oxides emissions! For that reason I might tend to steer clear of the most recent diesels. (I currently run a 2007 Cummins ISC (350 hp) in my RV and am so happy as I watch newer owners struggle with the DEF problem) Another caution is to keep the displacement up. You see 5.9 liter engines rated at 500 hp, and 8.3 liter engines rated at 200 hp. The lower rated engine will last longer. Also figure that most on the road tractors go over 500,000 miles before being traded--and many go a million miles before major overhauls.
I think the secret to the cold weather is a good block heater, and even a heater along the fuel system--plus cold weather formulated diesel to prevent the gel factor. Granted we have not lived in the arctic, but we did a lot of "ski camping" where the temp was below zero when we needed to start the diesel--and no problems. The other "secret" is good filters, plus frequent changes. Although it may be "overkill" we use a 2 micron filter after the 30 and 10 micron filters in the fuel lines before the engine filters and inception pump. We tend to fill up at truck stops or Marinas (in boats with diesel) with high volume, and avoid filling when the delivery tanks are low. In boats I used to have a mason jar we put the first bit of fuel into, and if there was clouding/particulate matter, we either went right to a 3 stage baja filter or did not fuel there.
Allison transmissions--sure there are a large variety--but they are made up to drive the heaviest of vehicles, including those with GCVW of over 100,000 lbs. (beyond what is sheet legal). Many of the on the road tractors now run auto transmissions. The 6 speed Allison in our RV is rated for up to 50,000 lbs capacity and over 500 HP. That exhaust brake is really great! Failure is rare.
There are also some good specific truck transmissions, and I really like the one in my GMC Yukon XL (gas)--but it is not a Allison! I do think that a tow haul mode is a great feature--since it not only tends to lock out overdrive, but in some transmissions resets the shift points.
Although you may not recoup the cost in fuel savings with a diesel (especially since diesel is currently more expensive than gasoline--no real reasons why), but that extra torque, and the exhaust brake make a huge difference when towing.
The Scan gauge was also mentioned--there is one available for diesel, and I think that everyone who is towing today should get one on their truck--they are only a little over $100, and give MPG, instant, average, various pressures, and temps; information you will not see on the analogue gauges, and you can supplement those numbers you see on the most modern trucks digital gauges.
