Actually, the service manual (2010 touring models) specifically tells you to add 32 oz for a tranny fluid change. It also tells you not to overfill, and that the capacity is 32 oz.

I've never had a problem when I change my tranny fluid, and add the full quart. The dipstick shows the fluid right at the full mark.

 

I just changed mine - dumped out the Redline 80w and changed it for Silkolene V-Twin transmission oil. To make sure I got out as much of the Redline as possible I stood the bike upright to get out the last couple of ounces.

It's good stuff. The transmission seems to click through the gears with a slightly more positive action than it used to.

 

The manual for my '07 Road Glide says 32oz. in the transmission. I just buy a container of Mobil1 75w/90 gear lube and pour the whole thing in. It's not worth sweating over 2-3 ozs. either way...