If im understanding you correctly, you either completely misdiagnosed the source of your shudder (shutters are on cameras or windows) or didnt attempt any diag at all. Just replaced the transmission?
Also who is "they"? Is this a shop, the dealership or someone else?

Misfires will absolutely cause issues with transmission and torque converter function and should have been fixed long before you replaced the transmission.

Did you replace the converter as well or just put the same converter on the replacement transmission? If "yes", how many miles on that converter at the time the trans was replaced?

 

Sorry, on pain meds for back issues so might not have explained throughly , sounds like you understood . They is the transmission shop. And no the “ shuddering “ was diagnosed by transmission ASE certified shop. I’m just trying to see if anyone has had this issue or could direct in the right direction. Transmission issues was tq” Torque Converter “ and valve body, clutches burning.

135k

 

If all you're getting is a P0300 and have a scan tool that can read ALL modules for codes, "B" and "C" codes too, then you need to solve for the generic P0300 which is for engine misfires.

You can access the shop manual for free at Charm.il or pay for an online subscription at AllDataDIY.