Lack of available information
I narrowed down the creator of the sound to eight individuals, all of whom were sound engineers or foley artists when work began in 1984 on the original Transformers cartoon, where the sound first appeared. They were:
- Jim Blodgett
- Michael L. DePatie
- John Detra
- Ron Fedele
- Michael Tomack
- Richard B. Elliot
- Richard S. Gannon
- Richard C. Allen
(See here for instance.)
Unfortunately, none of them have been interviewed extensively, nor have any of them written or spoken in detail about their sound work on the cartoon.
Unless one of these individuals decides to reveal the "back story" behind the creation of this distinctive sound effect, I doubt that an answer can be found at the present time.