It is an ACERT.
In October 2002 CAT stopped making "plain old c-15", and started to make "bridge", which was almost the same, but from what I've heard, worse version.
After October 2003, they started making ACERT(twin turbo)....

I have the same engine as you along with those 3.36 gear but I have a 13spd. It's a fine gear setup to cruise through the midwest at 65+mph and still get good fuel mileage, but as soon I hit even the slightest incline, I lose a tone of speed and have to eventually shift. A couple weeks ago I was climbing cabbage with 43,000lbs and even a heavy hauler passed me... When I decided to run the west coast only, I'm going to regear this truck for sure.

Okay, you asked for it: 6.9 mpg lifetime average in one of those "ugly aero peter cars".

Oh, really?????

I thought the ACERT motors said ACERT on the valve covers? My buddies 2006 Pete does, this one does not? I dont know, but I do know it gets shitty fuel mileage and does not pull worth a crap.

Yep, i have been running Oklahoma, Arkansas, Texas, Mississippi, and Alabama for the last month and am getting about 5.5mpg in this. I just got back home to the midwest today and averaged 7.1mpg from El Paso to Chicago :)

But again, the loss of power sucks bigtime.

But once I drop out of the 10th into 9th, it dont matter what I'm climbing it will hold it's speed.... guess this is typical with these motors...

All i know is when i was pulling 32K in the Pete, I could run in 13th and never have to downshift over many hills.

it's more about the gearing and not the motor.

Yeah, it's a different world comming out of a 700hp Mech CAT/13spd/3.90's to a 435 ACERT CAT/auto-10/3.36, just got to get used to this pooch.

i'm stlll wondering how you got a twin turbo with less than 500 - 550 hp on it... and if I was to go with a c15 twin turbo I would definitely go with the 1994 model

no such beast in 1994.. also theres many twin turbo trucks with a lot less then 500 hp

He has no idea, what he's talking about! Probably just a kid wannabe. In 1994 first 3406E was born, and first Acert (twin turbo) in 2004, 10 years later. I happened to have both of those "first born" engines in my trucks. 2004 is still running!