Ok this is a strange one. Have a 1975 4 speed all stock. When the temperature drops to 40 and below first start there is a rattle noise coming from the transmission. The colder it is The louder The noise is. The noise stops when you step on the clutch pedal. When the car warms up the noise goes away. Shifting is perfect and crisp. This does not happen at all in the summer. Was told it's the gear oil in the transmission, if it's cold out gear oil is very thick and it needs to warm up to lubricate correctly. Does anyone know what this is? Driving me crazy.