Why rpm jumps during accelaretion between 25mph to 60mph

Hello friends

I have explorer 2009

During idle the rpm is constant

During accelaretion from 0mph to 25mph the engine is smooth

During acceleration from 25mph to 60mph, when I'm in 1500-1400 rpm, it jumps to 1800rpm with rrrrr noise and go down back to 1500rpm.

Its happened several times until I reach 60mph, and then the car drives smoothly.

If I will accelarete with higher rpm, 2000rpm or more, the rpm jumping doesn't accure

What is the cause?

Please help

Thanks