i pulled the trans over the weekend and pulled the side cover off tonight. nothing seems out of place. How do I know what to look for? I rebuilt this several years ago and looks the same as before.I'm a little lost at this point

Check cluster for end play. Move it back and forth. Use your judgement for clearance, as I don't know if there is an actual spec. Excessive motion would indicate a thrust washer worn out. After that, I would pull the tail assembly off and check both main bearings, input rollers and spin cluster gear and listen for a similar noise to what you heard.

A lot of good members posting in this topic. I would maybe post in the question and answer forum also. Or you're in Ohio, as is Brewers. They'll probably be at the swap meet this weekend. Or just give them a ring. I've rebuilt mine and my dad's, but don't know enough to truly help diagnose your issue.

Why don't you clean up the spare tranny and pop it in? Its not that much work - is it? Yours is a 23 spline - correct?

Mark, because I would really like to find the reason mine is making this noise- there's not a whole lot to these transmissions and I'm still scratching my head.
I'm one of those people that need to know what happened,lol!
I showed it to Dan @ Brewers over the weekend: aside from the cluster washers being junk and the ends of the cluster gear needing machined, it all looks good.
He said there was some debris that has gone through it.
I'm sure this is a result of the shift fork breaking a year or so after I rebuilt it.
I'm gonna pull the scattershield and see if maybe a spring broke on the clutch disc.

I like the idea of the front or rear bearings being the noise. Always thought gears would make a whining noise if loose. Check the u-joints too.

So Dan @ Brewers said the cluster washers were worn. Did you check out the YOU TUBE video on the 833 making noise? If the washers are worn the cluster gear will move back and forth hitting the sides of the gears on the main shaft as I posted earlier.

I suspect that you are going to find something fouled up in the clutch. Something that causes intermittent disengagement issues. Maybe a broken spring, cracked disc hub, lining delamination, etc. Check it over good.

If you take it to Smythe Automotive in Westchester, Rob Nixon will inspect it for you.

They are not too thin, just full of trash which scratched up the cluster real bad. Trans was dis-assembled when I looked at it but I doubt it has more than .025" endplay even with the washers bad. I suspect at this point something in the bell also, the noise is not always there. It can come or go, even in the same gear.