Have a 1997 4700 dump with a DT466 and this one is not an E-model (Mechanical fuel shut off and injectors). Has the 6 plus 1 tranny. and a single speed rear axle. It is a 26K no CDL truck with a 38K tag on it. Last year I could haul 10 ton of rock up a mile long hill and have to down shift to 5th 3/4 of the way up. Put my 10 ton tag trailer behind it with my CAT 416C extenda hoe and I need to hit 4th before the top of the hill. This year I've been running dirt pilled high and I have to hit 4th to finish pulling the same hill. I had about 2K miles on the fuel filter but chauged it out just to see if it would help, it did not help. It does a little chuging every so often under heavy load but not all the time and runs flat out with no load. Sure could use a few more ponies back, any ideas?