shifting woes

[4.0=SS]

What trans fluid are you using. What do the pros here suggest?

[Banjo2010]

I hope you got this figured out; but if not, here was my experience:
I rebuilt my TR6060 myself, with mostly the same goodies inside, and an MGW. Monster twin disc clutch, and mine would nibble and catch, mainly in 1-2 gear. I swapped factory shifter and clutch back in (lots of wasted time) with no change. Long story short: GM synchromesh is not a good match for aftermarket carbon fiber synchronizers. I use Redline D4, or you could use ATF. Anything thicker viscosity doesn’t let that ring grab. Carbon fiber friction material is desirable in aggressive use(in this case, hard/fast/high rpm shifts). They have to get slipped/warmed to grab. If you want butter smooth shift at low rpm, bronze is a better material.
I was afraid I goofed mine up, but finally after putting the twin disc and MGW back in I just ripped on it for 3-4000 miles. It has smoothed up to the point of being pleasing in every gear but 1st, from a stop.. It is not a clutch issue. It has to do with those synchros. The bronze bushings combined with the MGW mounting system means MUCH less deflection between your hand and the teeth on those gears; so nothing is “flexing” and cushioning/redirecting the force of gear selection if the gear isn’t just perfectly lined up. I know this is the reason for my issues, because if you rev the car up to 2000rpm or so, then clutch and press 1st gear pretty quick, it’s smooth as silk. I know companies can probably build a tr6060 with the same stuff and get a smooth shift sometimes, but based on reviews it’s not every time so don’t worry about it too much; just swap to a thinner fluid and drive it like it’s 1967 for a bit. Good luck!