for the tranmission, the modulating valve is the first thing you would want to measure and adjust (using a pressure guage). if it does not work, you would need to check your fluid and trans filter, while on it, I would suggest to have your valve body serviced. Those are the basic cause or symptom of a tranny going sour. You'll need a complete set of rebuilding kit consisting of gaskets and o rings. Normal for a 126 to have it service after a long miles of service.