I have a 1980 malibu with a 350 transmission and open diff rear end. My car makes loud clicking noises when i change from park to reverse/drive or reverse to drive etc. also makes click when i accelerate hard. there is about 3-4mm of up and down slack where the driveshaft meets the differential. Would it be a good idea to tighten up the pinion bolt and drive on the axle for a few more years, or is it too far gone? other options?