traviling on highway when I reach 65 a loud grinding noise starts I push the 4w high button and the noise goes away and when iI go back into 2wd the noise will be gone until I reach 65-70 mph, very enoying since I drive 100 miles per day on highway, I forgot to mention it is a 3 button NV233 ? transfer case. all help would be great

 

Sounds like your front axle might be trying to engage for some reason. I would look at the vacuum actuator and cable for the front axle to make sure that everything is releasing properly when in 2HI.