Outer Limits 4x4 Board

Hi,I have a 89 hilux that had a 2.4 with a auto and i have swapped the motor for a 2.8 and within a month it cracked the flex plate where the torque convertor bolts on.
I have replaced the flex plate and it lasted 9 months but has cracked it again. Everything was torqued to the right setting when it was installed, has anyone got any ideas
why it would be doing this?

How do you tell if its cracked before taking the thing apart? My cruiser has some noises coming from around there and people suspect its the plate.

A few things we see all the time are-

Dowles between engine and transmission are missing even just one, the Torque Converter does not pull up to drive plate flat,Converter spigot is wrong size for crank,dive plate or spacer installed the wrong way.

would driving around in overdrive all the time cause this?

My hilux has a little access hole on the dust plate behind the sump that you can look through and see if it is cracked