I have a 94 Z28 which does not want to downshift at all unless you manually shift it. It still upshifts fine but will not downshift at all. Any suggestions on what to check for before taking it to a shop. Some one said I should check to see if its throwing any codes out but I don't have a code reader yet so if you have any recomendations on where I can pick up one relatively cheaply, that would also be very helpful. Thanks.