Looked at the valves and chain...everything looked cool. The tops of both guides looked okay. Both the top gear and lower one that you can barely see looked okay. I turned it and had my buddy watch the lower one with a light. Valve clearance was all good....number four was a little tight on the intake but i didn't move it as it hasn't had a problem yet.
I have considered the tranny as I've heard a cranking sound come from a Nissan I trashed.......crappy Nissans. This goes along with not hearing it when in neutral. I rebuilt the tranny about 40k or so back....replaced 5th gear, all bearing and seals but I reused my old synchros. I got a w56 in an '81.
What about the rear end....I've never really been around a bad differential. My rear end has popped a few times when taking off, but not very often and happened before I heard this new noise. Also I wouldn't expect a differential to make rpm depended noises.
I will change oil over weekend and see if anything is in it. It needs to be changed anyway. I need to get a decent filter so I don't get that dry sound initially after cranking.
Thanks for all the suggestions. Maybe we'll get this figured out......or I'll drive it till it breaks one.....I guess we would figure it out then too....ha ha.