The term semi-float isn't quite correct for the light-duty Sterling, as it usually refers to the 9"-type axles with the pressed-on bearings, which the LD 10.25 lacks. Instead, the LD Sterling is set up exactly the same way as a 8.8 (only everything is obviously much larger) - it uses C-clips to hold the shafts in, and roller bearings on the wheel side that use the axle shafts as an inner race. Interesting thing is the center section is exactly the same as that of a full-float Sterling, so any differential that fits the full-float will fit the LD as well - as evidenceed by someone we know currently running the old Trac-Lok out of our dually in their F250 with the LD Sterling. But, again, it is NOT an 8-lug 8.8 axle, such a thing does not exist - it may look like it, but it's a 10.25" Sterling, 1.5" 35-spline shafts and all.Oops just reread the last sentence of your post. So a semi-floating 10.25 is missing that awesome giant hub, eh?
Mine was possibly a 10.25....hmm..
How much would a full floater increase the payload by?
As to how much payload the full-float hubs add - well, about 1000 lbs. A typical full-float 3/4-ton 10.25 Sterling will have GAWR of up to 5300 lbs (as per the owner's manual for both bricknose and OBS trucks), whereas the LD Sterling without full-float hubs has GAWR of slightly over 4000 lbs (actual off the ID tag in the cab). Bear in mind the axle codes are somewhat generic, they list the model of axle (8.8 or Sterling or Dana) and the type of differential (open or limited-slip) and the gear ratios, but they do not differentiate between a LD 3/4-ton Sterling and a the full-float 3/4-ton Sterling - both axles will get the same first character ("2" for open diff and "B" for LSD). Same applies to the owner's manual actually, the table in its towing section is only for reference as it lumps both 3/4-ton Sterling axles together. Also the GAWR is not determined solely by the axle type, the springs also come into play - for example a 1-ton SRW Sterling will have a GAWR of up to 6250 lns (as per owner's manual, which is full of sh*t as the wheels and tires are only rated at 3042 lbs each so 6084 total, and that is exactly what the cab tag will show as well), yet the exact same axle assembly when rolled under a 3/4-ton truck loses almost 1000 lbs in GAWR - those 1000 lbs come not from the axle (or wheels and tire size), but the springs. So your general pattern for SRW Sterling GAWRs is as follows: 4k for the LD 3/4-ton axle (hubs-limited), 5k for the full-float 3/4-ton axle (springs-limited), and 6k for the full-float 1-ton version (limited by the housing & wheels /tires).