’06 Acura MDX tourque converter shudder at 40mph

Ok , I have a tourque converter shudder at around 40mph, was told it is a bad torque converter, apparantly a common issue in the MDX. Question is do i replace the converter with a oem unit, or should I go with an aftermarket if aftermaket what brand quality?. Also searched internet and guys are saying to to change fluid 3×3 method and on the third flush add the third quart of honda vtm diff fluid that should solve the issue 90% of the time. Is that safe? No shudder in D4 , so lately around town I’ve been driving in D4 . I would like to tackle this issue but kinda don’t know which direction to take. Definatley would like to start with least expensive.