So if your weights in the trailer was not changing much like carrying water in the waste tanks to cause a change in sway then maybe your sway control was changing somewhat day to day. Possibly the weather was changing too. I think some of it might ...
Is the 6.4 even on the dealer lots yet. It appears you cannot get the 6.4 with a 4.10 gear ratio. I don't think 4.10 is as important with the gears on the 6 speed compared to the 5 speed in the past.
The bottom of my plate is 49". I think most semi-tractor are not that far from this height. Pulling a couple inches high or low to get it home will not matter much.
I assume you did not do something like putting the rear stabilizer jack down first. That would make it slow down a lot. They are not all that fast anyway but you might need to check the electrical connection to the jack motor.
