What's odd about the 44-tonner is that while they did a great job with weighting up the fuel tank area they left the cab area empty. So the simplest thing to do is stuff whatever you can into the cab area, probably on the shell itself.
This is one of those mechanisms you have to test and tune. I test and tune mine on an Atlas C80 #6 crossover, which has alternating dead spots long enough to cut out each truck one side at a time - forcing the other truck to pick up or shut up, so if it stalls, its painfully easy to see what is NOT picking up properly and put your attention where it needs to be.
Mine works great, way better than any other tiny critter I own and pulls respectably. But I weighted up the L out of it in the cab area. You don't need to do weird pickup stuff, its already 8x8, just get as much weight in it as humanly possible.
I also jerked the entire DCC board out of mine as my transistor DC throttle hated it in 17 different ways. It sure ran better on DC without the board than with it in there. That board might think it is dual-mode.....
Their 70-tonner put me out of the 70-tonner business pretty quickly, but the mechanism is still much better than Kato's - better pickup, slower speed, better tractive effort. It's not so complicated that you can't tinker with it. The most inexplicable thing is that the entire unit is way too wide even though the motor is narrow enough to fit in a scale-sized hood. I've accused Bachmann of using the HO models for reference rather than looking at real drawings, but that mechanism is pretty much as good as it gets in critter world.
