I am pulling 0 to 37 amps through a 55 amp mosfet, P55NF06L. I have very good aluminum heat sinks they are not getting hot with heat sink compound. The mosfet is ok with 37 amps for a few minutes but it will not do 38 amps more than about 3 seconds. Current goes through pin 1 and pin 2, but the tab is the same at pin 2 so maybe the tab can handle more current than the pin? I have not tried running current through the tab yet. I am a little bit surprised the pins can actually handle 37 amps there physical size is about = to #18 copper wire. Pins are solidered to #10 solid copper wire the copper wire can be heat sinking the pins too. This is an educational question to learn about mosfets. I think this circuit has reached its limit, time to do something different. I need to learn and have a better understand why these mosfets go up in smoke at 38 amps?