Many Uber drivers are in it for a few extra bucks. Michael Grimes has a bigger prize in mind.

Grimes, Morgan Stanley’s top technology banker, has moonlighted for years as a driver for the ride-hailing service, according to people familiar with the matter. That side hustle—hardly necessary, given his multimillion-dollar Wall Street salary—may help Morgan Stanley win a role on the most hotly anticipated stock-market debut in years, The Wall Street Journal reported on Thursday.