Hi everyone i have 72 z made in late 71 i get some noise out of the rear end when i shift any advice on this , sounds kinda like a band or a klunk not sure what it is schould i use a heaver gear lube and would that help thanks .. houston

Welcome to the site! Apparently this is a fairly common noise that our Z cars make. From what I understand it can be a couple things like diff mount bushings or u-joints. I am guessing you also hear going on and off throttle if it's an extreme enough change. The actual diff and gears are quite durable.

If you search "differential clunk", you'll get tons of threads that will have ideas.

As someone will surely ask, have any pictures of the car?

Houston, I see you also left a visitor message in my profile. Andy pretty much hit this one on the head. There are a few things that can lead to this but when we hear the word "cluck" used to describe a noise in the rear on acceleration, we generally think of the front diff mount isolator. This is a rubber mount much like a motor mount and prone to failure due to age or abuse from quick launches etc. These mounts run around $45-50 and are available from several sources such as www.courtesyparts.com, www.blackdragonauto.com, www.nissanparts.cc, ebay, etc.