Used car dealer sold a car that died 40 days later. What can we do?

What do you all think about a California used car dealership, selling a used
vehicle to an 18 year old, & 40 days later the transmission is blown.  We
went to the dealer to ask them to fix the car and do right by my son who put
all of his money and faith into this car purchase.  The dealer basically said,
you bought it "as-is", and once you take ownership of the car, it could last
any amount of time.  But 40 days, come on!  My son bought the car "as-is",
but isn't there an implied warranty merchantability?  What should we do?