SM465 Gear Knock/Tick????

[Jimk20]

Hello everyone. I have a 72 chevy k20, sb350-sm465-np205-dana 44 front-14 bolt FF rear. Just picked this truck up a couple weeks ago and it's my "new to me" daily driver (I know, I know, what am I thinking). Anyway I'm in love with this truck but I'm starting to have some transmission concerns.

A couple days ago I started noticing a knocking sound/heavy ticking sound. This only happens when I'm DECELERATING, clutch pedal DEPRESSED (clutch disengaged), and going under 10 or so MPH with the transmission in or out of gear in ANY gear (except for granny low, never tried it in low gear before). It might make the noise all the time for all I know, but the truck is loud and the trans knock is only audible when doing the above things mentioned and the engine more or less idling. Also, you can feel this knocking sound in the shifter. It's a steady, rhythmic knock that's always there when the truck is coasting slowly. As of now, im not worried about it. I've driven trucks before with 465 trannys and I know how rugged and durable they are. It just bugs me because the knocking sound is kind of loud, loud enough that when I coasted next to a fellow motorist on the highway, the old man told me "Beautiful truck, but what the hell is that noise?"

Like I said I'm not worried about this issue, unless I should be hahhah. This truck is an animal and its driven at least 30 miles a day for work, both highway driving up to 65 mph and in town driving combined. On the weekends I'll take it for trail rides in the NJ Pine barrens, and even going in the woods doesn't make the noise worse, or better for that matter. My names Jim and I'm new to this forum. Any help to my issue is really appreciated.