You're welcome.
There are sort of two separate but related things. There is Tongue Weight, which is what you would measure if put a scale under your tongue jack, and there is another thing, which some people seem to call "Hitch weight" or "Receiver load", which is what the receiver of your truck sees.
Tongue weight is important because it shows how your cargo is balanced in the trailer, and receiver load is important because it shows how much weight is on your truck.
The weight of the WD Hitch assembly is the difference between these two weights -- the receiver sees not only the tongue weight, but also the WD assembly weight.
From your scale weights, we can figure out the "Receiver load" -- it is the difference between the empty truck weight and the truck weight with the trailer connected (Tongue weight + hitch weight: 1240 (3620+4880) - 7260). If you had put the WD assembly in the bed of the truck when you weighed it empty, then we would would know for sure. What we do know is that when you added the WD and the trailer, your truck got 1240 lbs heavier -- and we know that some of that is from the WD, and some is from the trailer.
Since we don't know how to split it, I guessed. If the WD assembly weighed 0, then the tongue weight would be all of the 1240, but we know that isn't right.
If the WD weighs 100, then the 1240 is split 100 to WD, 1140 to trailer -- I did that for 50 (+1190 = 1240), 100 (+1140 = 1240), 150 (+1090 = 1240) and 200 (+1040 = 1240), since I figure your WD probably weighs somewhere in that range.
Let me know if this made it more or less clear....
Bret
