Need a lot more info.
Sounds like you have the same downshift jerking problem that half the people with built trans I know have. Mine does it bad and has been doing it for over 100,000 miles of 550-650 hp. I have had it to downshift hard enough to squall the tires. No codes, no trans slip nothing, acceleration is smooth as butter.
I have replaced the transfer case speed sensor. I have also replaced the slip yoke with a nickel plated one, nothing helps. I think these built transmission are just tight enough that sometimes on a downshift it suddenly takes up any slack in the driveline causing it to jerk. The weird thing is some of them don't do it, I don't think your ever going to get a straight answer on this.
Raybesto GPZ clutches and it was built around 5 years ago.What clutches are you running and when was the trans built?
That's good to know mike, I changed the fluid very soon after it was built and then about every 30-40,000 miles after that, and I change the internal filter every single time. Spin on get's changed about every 15,000.Change the internal filter as those clutches tend to shed and restrict filter. Dex 3 is fine.
Please update with what you find.