My Jatco is slipping in 1st and 2nd when it is hot, when it's cold/warm it's fine..only does it when you drive car hard for half hour and the trans heats up..guy told me it needs oil change and filter...you can smell oil/burnt oil when trans is hot. Any help/ideas why it slips when hot??

maybe start with changing the oil and filter and upgrade to a bigger auto trans fluid cooler