Ok I got vacuum at the front diff for four wheel drive it's a faint suction. Vacuum gauge is going on it tomorow my question is how much vacuum am I supposed to have on the three lines when I test it. My modulator on the front diff might be bad.

 

It won't be as much as at the motor due to the nature of the leaky vacuum switch. It leaks so that the vacuum can bleed back to normal when the other side is switched.

 

I just installed a new vacuum switch it's normal to reduce suction at the switch? Better yet how Much vacuum from the 3 modulator lines on rhe diff should I have on the gauge