Terminal 4 to 8
 

what is the best way to reach terminal 8 from terminal 4 to get a connecting flight at JKF Airport

The AirTrain connects all the terminals together. Make sure you are on an inter-Terminal train, rather than a train away from the airport.

Actually, from 4 to 8, you can take either the clockwise inter-terminal, or one of the counter-clockwises that go to the parking areas. Still 3 stops. Virtually same distance. So, just jump onto the very first train that gets to the T4 station.

I mean "or one of the counter-clockwises that go to the parking areas AND Jamaica/Howard Beach."

I made the same transfer and unfortunately you cannot stay airside.

rk has it correct. You can take a train going either direction and you'll get there in the same time.

There are 3 train routes on 2 tracks

Two that run counter clockwise and go off site after T8. Those are the Howard Beach and the Jamaica trains. They run a T1-2/3-4-5-7-8 then off airport order.

The 3rd train runs clockwise and goes to all terminals in T8-7-5-4-2/3-1-8-7 order