Had the same issue with my 05FLHT. Dropped out the primary and trans fluid and replaced both with full synthetic Redline. The primary with Redline MTL Manual Trans Lube and the trany with Redline heavy shockproof. Made a big difference, really helped with the hot weather loud shifts and did reduce the 4th gear wine also.
PS the HVY shockproof looks like thick tomato soup!
