Like another questions it seems the transmission drops out for a second,

keep going ,trans is probably going

Not enough info. But if you are moving that fast it is likely not second gear. Could be a failing overdrive clutch, TCC lockout solenoid. Torque converter, or an electrical issue. If the check engine light is on that may help.

your described conditions almost sound like hydro-planing , not trans. does the symptom occur on dry roads?