The force stopped the vehicle on the M1 in Rotherham earlier this week.
A spokesperson for South Yorkshire Police’s Operational Support Team said the driver was initially stopped for using his phone while driving.
Posting on Twitter, the spokesperson added: “This then turns up the fact he has no licence or insurance.
“Subsequent stop/search then shows up circa 8k hidden in a carrier bag.
“Driver is arrested on suspicion of money laundering plus driving offences.
“The vehicle was also seized.
“Yet again, all that from a simple traffic stop.”
A member of the public asked the Operational Support Team whether being found that sum of cash was enough evidence on its own to be arrested on suspicion of money laundering.
The spokesperson replied: “There's more to it than what we can post.”