95% of the time I'm between NJ, NYC, and OH. 40% of my mileage in a hills of PA, usually, I'm not heavy, I'd say my average load is about 25,000lb.
But i do a lot of 2 lanes with some lights, and of course, you know how NYC is! :shock: :D

CATs and especially ACERT, very sensitive to RPM "sweet spot" and don't like "pushing", you got to be very gentle with it. "Sweet spot" for ACERT, is around 1325 RPM, according to my ECM, I'm between 12-1400 77% of the time. It has plenty of torque on the lower end, don't be afraid to use it.

I've just delivered 40,000lb load on I-80 from OH to Brooklyn, NY with my cruse, set at 65mph, only had to split(13) once, didn't even pushed it before the hills. 8)
http://i6.photobucket.com/albums/y213/solo3793/cat3.jpg

thanks. that's where we run too. up and down I81.

It's also going to depend on the hill. The hills solo pulled may not be hills like you'd run into in the mid-west, west coast region. Hell, I just had 48k lbs on, and with my 475 c15 (non-acert) 13 speed, and lp 24.5's with a 3.55 rear, there were many hills I held speed on, or could accelerate on..but then there are your hills which will drop you to 30mph in a heartbeat..you'll literally drop like a brick...NO amount of "pedaling in the sweetspot" is going to save that. You CANNOT pull 80k lbs, up a 5-6% grade at 65mph with only dropping 1/2 a gear, or a full gear...unless you've got a worked motor, or maybe a pre-emission 600 cat...that's running lp22.5 rubber and 3.90 gears lol

No, you can't! And i didn't say that. But before that ACERT, I've had a 3406E CAT and my current 475 pulls even better, than old 550, on the same roads.
And even with some gain in fuel economy.
That's all I've wanted to say.