Well, went and looked at and tried two LB7's this weekend. One had 120,000 miles, and had been plowed, and one had 145,000 miles and had never been plowed, both were 2003's. The 120,000 mile truck had injectors and such replaced at like 25,000 miles, and seemed to be much more laggy on the fuel compared to the other truck which has just had injectors and pump replaced 6 months ago. The 145,000 mile truck, as soon as you hit the fuel everything was right there, RPM's would go right up, and you could feel it had more snap than the other truck I tried out. I assumed it was because the pump and everything was so fresh and the other one was more worn out, is this possible?

As for the plowing thing, the 12,000 mile truck seemed to slam more into gear. On the highway doing like 55, you would hammer it to the floor, and it would downshift, climb to 65, and slam back into gear, you could really feel it. I don't have much experience with the Allsion, but I know that I have a 15 y.o truck that shifts smoother than that. Is this a sign that the transmission is worn from plowing/heavy hauling? Through all the gears, it just seemed to not be really smooth. Even the 145,000 mile truck I tried didn't seem real smooth, I mean it was a lot better, but not exactly what I was expecting.

I am no longer interested in either of these trucks, but I am just trying to learn more based on these two trials.

Thanks, Jacob

Moved to Buying a new truck.

maybe the one that had 120k on it had a tuner on it???? caused some tranny issues

The 120k mile truck probably had a shift improvement kit installed. These actually extend the life of the trans by reducing the slipping during shifts that many people misinterpret as smoothness. The manufacturers build the transmissions to slip on gearchange to reduce NVH because people erroneously expect trucks to behave like cars.

The 120k mile truck probably had a shift improvement kit installed. These actually extend the life of the trans by reducing the slipping during shifts that many people misinterpret as smoothness. The manufacturers build the transmissions to slip on gearchange to reduce NVH because people erroneously expect trucks to behave like cars.
The Allison is designed to be a very smooth transmission without shortening its life at all. Even race built Allisons are pretty smooth. If an Allison is slamming into gear, something is wrong with it.

Case in point: my transmission has 245,000 miles on it with nothing but fluid & filter changes. It is so smooth that people can't feel the shifts at part throttle. Even at full throttle, the 1->2 and 2->3 are imperceptible, and the only reason I feel the others is because of the defuel, giving the impression that I let off the throttle mid-shift (because that is what the truck is doing). There is absolutely nothing abrupt or harsh about the shifts; even wide open, they would probably be described as "soft" if anything. Interestingly, that "soft" spot during the shift (defuel) is still putting more power to the ground than stock...

One possible explanation for the trucks is that they were tuned, and recently returned to stock, without resetting the TAPS. That would cause harsh shifts. Or, they did reset the TAPS, and it hasn't learned yet (it takes a few days to relearn). That also causes rough shifts.

Although my guess is the trucks are both beat. I test drove dozens of duramaxes before buying mine, and 75% of them felt like they had 500,000 miles on them, even though most had less than 150k.

Final thought: go test drive a stock '06 Dodge Cummins at full throttle. If the Allison shifts are even half that hard, it is toast.

They were both supposed to be stock, but the $120,000 mile truck was worked pretty hard for sure, between plowing, and towing fifth wheel, and trailers and such.