what defines a 3/4 ton?

philh wrote:
If it's payload capacity, then why isn't a properly equipped F150 considered a 3/4 ton truck?

The OP question was 2 part.
His opening line was "what defines a 3/4 ton truck ?

Then compares it to a a payload capacity from a properly equipped F150.

Payload capacity in todays high 8200-7850 gvwr F150's can and have caused overloaded rear axles especially 3100-3300 lb pay loads are placed in the bed like a truck camper or pin or bumper hitch loads. One truck camper owner found this out the hard way when he bought into his F150HDPP 2982 lb payload sticker.
The F150HDPP has a 4800 rawr which is small and limits it to approx 2400-2500 lb payload in the bed.

Enter a 3/4 ton with its much heavier duty full floater rear axle that has carried 6000-6500 + lb RAWR... 6084 lb back when the C6P chassis was the HD line in the '80 era.
The 3/4 ton truck rear axle is good for up to 3200-3400 lb in the bed payload so ....

Fords F150HDPP doesn't match up with any 3/4 ton trucks real world payload numbers.