My tranny is downshifting out of 4th gear rapidly sometimes, it downshifts real hard and jerks real bad, then sometimes it shifts like a brand new tranny no problem. I can put it in 3rd gear and it stops the downshifting. I can put it in manual shift and it will not go into 4th gear. but when it is working good it will shift through all gears no problem. It just started this after a head replacement and the battery went dead during the process, any clues and how to check this out? It has the accelerator cable not fancy drive by wire tech. Please help I love my car but I think it might downshift one day at 70 mph and blow up. Thank You Ken