Ram 2500 4x4 coils

From : jlake

Q: if you can hear a flap or something shutting in the vent system then it is probably a check-valve of some sort or a loose vacum line. i had a similar issue on my 99 ram 1500 4x4. every time i acclerated hard the dash vent would shut down until i eased up on the throttle and the front axles for the 4-wheel drive wouldnt engage. my problem was a vaccum line that connected the auto locking 4-wheel drive and the a/c vents was disconnected. .