Ford 1996 Windstar Manual page 256

Subtract vehicle actual weight from the GVWR to find out
4.
how much more weight your vehicle can carry.
Weigh the vehicle again once it is loaded to make sure that
5.
the GVWR and front and rear GAWR's are not exceeded.
Trailer towing table
If you suspect that your payload is excessive, have your vehicle
weighed at a highway weight station or another appropriate
commercial facility. Fill the fuel tank. Weigh the total vehicle
and trailer (if applicable), then separately weigh the vehicle at
the front and rear wheels. Finally, weigh the trailer separately if
applicable.
Trailers
Towing a trailer safely means having the proper weight on the
tongue (usually 10-15% of the trailer weight).
If your vehicle exceeds the GVWR, remove cargo from your
vehicle accordingly. If your vehicle exceeds either GAWR, shift
the load or remove cargo accordingly.
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