I just flew from KY to Cali to drive back my 86 El Camino that is powered by an 87 GN power train. The car has been sitting for about 18 mos and before i parked it, it ran and drove perfectly. Now the car will not shift gears. It stays in first. Ive changed the filter and fluid but that didnt help. Ive got 2 days to get this car fixed or ill have to leave it. Anyone have any ideas what may be wrong. Thanks in advance.