The musicians who played on Detroit era Motown recordings are listed here:
The Funk Brothers - Wikipedia, the free encyclopedia
For post-1962 recordings, if you hear a tambourine, that was Jack Ashford, which means the vibes were probably being played by Jack Brokensha. Before 1963, or on tunes with no tambourine, the vibe player could be Ashford, or one of the other two vibe players listed on the linked page.
Read the book and see the movie "Standing in the Shadows of Motown".
Ashford is still alive. Brokensha, whom I met, died last October 28th, age 84.