T/A'01

I've got an 01 ls1 t56 manual 109,000 miles with a slight whine that mildly start at around 2500 rpm's and stops when i push the clutch in and it was slight hard to put into gear in all gears .

I changed the Trans fluid and put Valvoline synthetic blend in (before i found out about the blockers) it only ran in it for about 40 miles or so, but when i changed it, it shifted like butter, then the "40" miles or so went by and the whine started coming back slightly and it was getting hard to put into gear, so i changed it again with DexIII/M from advanced auto parts, whine went away but it was still slight hard to put in gear. im not sure but i think it's a lubrication prob or something, i don't know much about transmissions.

Anyone have any idea what the deal is?