Hard 40 mph shift in 65 tow

[Highbeam]

I ran around empty in the 65 tow tune last night trying to figure out just which "shift" is so hard. If I accelerate lightly I can feel the 1-2 and then the 2-3 nice and soft but then bang at 40 mph or so. After reading about this it sounds like the TC can lock in 2nd or the trans can shift to third and then lock up depending on throttle position so what I feel is the 2-3 shift might just be the TC locking in second.

Either 1-2-TC-3-4 or 1-2-3-tc-4 is how cleatus posted.

So, I'm not sure which shift I'm feeling but at about 40 mph it bangs hard when towing 7500. Not so hard when empty and at low/moderate throttle. Almost like the truck can accelerate from the kick vs. absorbing the kick.

I don't feel it as hard in the DD tune or the 100 perf tune. Haven't tried stock. If the hard shifting won't hurt anything then I can try it for awhile but if I had horses in a trailer I would NOT want that kick. It 's a leg breaker.