Mark,

I pull livestock for an outfit that buys many of their power units from a fleet. Ergo, they are fleet spec'd, and often identical.

About 8 years ago, we had two identical FL120's (97 models?)with the exception of power-plants; one with a N14, the other with a M11. Both had 13 speeds, same rear ratios, and 22.5 rubber. They would both run 55mph @ 1500 in 12th.

Our weights are usually in the 80-90K bracket (80 in the US, and we're allowed 87K here in Ontario).

Bottom line, to run 100 kmh (62mph) in Ontario and most US states, I'd run in 13th @ ~1500 on cruise. Long trips down to Indiana, I'd clear customs/USDA, I'd set the cruise and relax for a couple of hours, unless I had the M11. It may have been rated the same HP as the N14 (370), but only in some Cummins engineer's dreams. We suggested that the N14 had 370 horsepower, and the M11 had 370 ponypower. There was no comparison in terms of lugging. Often, when loaded, we'd end up running the M11 @ 1700 in 12th to navigate undulating territory, and occasionally it wouldn't hold speed coming home empty.

The owner of the fleet had said that they'd experienced the same thing. Net/net, I think there was 600 lbs difference in weight (and payload), but fuel economy was about identical because the M11 had to run spooled up more often to hold speed. Their fleet speed was 55, and they often couldn't hold that if you said the word 'grade'. Even though there was a slight positive bottom line to this engine in his application, he couldn't get anyone to willingly drive them. The same also applied to our outfit as well; the M11 took more effort to operate, and was louder in the cab.

If this is to be used for short hauls out of the field, and some 30-60 mile trips to an end-user, it might be OK. Unless it is somewhat discounted to a N14, I'd leave it. The N14 will run easier, not consume anymore fuel, and be cheaper to fix in the long-run.

My Opinion,

Luke    aka Ken SWOnt