My 78 Sierra has a 350 and it starts to tick from time to time after it warms up. It seems to get less noisy if I put the engine in neutral while idling. It sounds like it's coming from the engine and not the tranny. I first noticed it after I towed home a 68 c-10 about 150 miles with a car dolley. The truck is running good otherwise , I've just noticed this tick recently. Any one ??