Deductions & credits

I purchase my leased business vehicle and then traded for a new business vehicle that I paid cash for?  Please advise how to enter these transactions in Turbo Tax?  I use the vehicles 70% for business. How much 179 deduction can I take on the new vehicle (as long as it does not create negative income). Is it 70% of the purchase price? Turbo Tax gives me a number that is less than that amount.