Fernando Rivas took sole control of Wells Fargo's corporate and investment bank at the end of January.
The question of when Dimon will retire, and who might succeed him, has hung over JPMorgan for years.
The bank has been expanding its presence in midtown Manhattan recently.
He added that the U.S. economy is in a good place.
Its trading revenue came in well ahead of estimates, boosted by the volatility tied to the U.S. elections.
Trading revenue at the firm rose 21% from a year earlier.
The moves mark the latest major shakeup atop JPMorgan.
Mandell Crawley is a 32-year veteran of the firm and one of its senior-most Black executives.
More than half of the bank's roughly 300,000 employees already come into the office five days a week.
Markets whipsawed in the quarter as investors raced to analyze each new piece of economic data.