I swapped a 60e for 80e with a 3600 converter + HD2 kit and have some problems.

I have been trying to chase this with tuning but im starting to think its something around the HD2 kit accumulator springs maybe?..

Shifting up through the gears is fine from a dig with decent throttle, but a 2>1 or a 3>2 (mostly 2>1) down shift by foot will sometimes work great and other times shudder / vibrate violently that instantly makes you lift in fear that something is going to come apart.

I also have noticed that sometimes a manual 1st selection is not instant. It almost feels like it takes a second or two to accumulate enough pressure to engage something, but when it does decide to it works fine. Im worried this is whats happening during the 2 > 1 shift but I have no idea where to start troubleshooting this.

as said before it will run through the gears and hold like a champ 1>2>3>4 if its under upshift conditions.
When you mix in a downshift condition is when it gets all violent and wishy washy.

Any help would be appreciated!