I would have to say for a class 7 truck the Cummins ISC 8.3 is the best thing out there. It is a medium displacement wet sleeved engine that has proven itself to be worthy of both city and highway use, gets good mileage, and is inexpensive to repair and rebuild. There have been some problems with early ISC injector pumps, but I think Cummins has these issues solved. It is strange that the ISC still uses a separate pump-line-injector setup, where most diesels now use unit injectors, but as long as it works it doesn't matter.
Another good class 7 engine is the DDC series 50. It is a 4 cylinder version of the proven S60, but unfortunately is has only been available in the Freightliner FL106.
For class 7 Internationals, the DT466 has a really good reputation. It's a wet sleever too. It's tough, but many feel it lacks power.
I do not recommend parent bore CAT 3126's or Cummins ISB 5.9's for expedite highway truck use, and have not seen too many Isuzu or Mitsubishi diesels last too long under highway use either. But I will say the ISB is probably the strongest parent bore diesel in the world.
For a class 8 expedite truck, pretty much anything goes..CAT C10-12-15, Cummins ISM,ISX, DDC S60, any Mack, etc.. all are powerful and last a long time with proper care. I don't know of any big truck engine that has a reputation as a lemon.
As far as trannies go, the only horrible one I know of is the Spicer 7 speed job. That thing blew- literally! If you ever get the chance to see one and how physically small it is you'll understand why. Some of them actually threw parts right through the outer casing when they decintigrated. If you want a syncro, stick to the Eaton 6 speeds. They are tough.`I beat the hell out of the one in my old FL70 and it never had to be pulled for any service it required.
For class 8 non-synchros, I think Eaton/Fullers shift smoother than Rockwell/Meritors do, but they are both tough units. I don't have any personal ownership experience with the automatics.
-Weave-
