Not necessarily.
Pendy in the US has done lots of tdi conversions with the V8 ZF
300 tdi in a 97 automatic - The D-90 SourceQuote:
I use the V8 transmission it is stronger. Reconfigure the bell housing, adapter, retune torque convertor and replace govenor. All changes that M&D engineering UK helped pioneer to bring auto to these diesels and the powerstroke version. The correct transmissions have inherent problems as much or more then the converted V8 models in my experience.

