Gas pedal knock on hard acceleration

[LITTLEELVISDAN]

From a stand still in 2 or 4 wd in off road mode on. floor gas pedal on washboard dirt road and I get an intermittent knock feeling in the gas pedal. No where near the rev limiter. in manual shift or auto shift mode.

Is this normal and if so what is it. If not WTF?

I have never felt feedback in the gas pedal.

If I had to describe the feeling, it feels like a break pedal when anti lock kicks in. but its the gas pedal.