Hey! ive been having problems with vacuum getting to my 4WD and inside the cab.. Cruize works perfect, but 4WD engages after about 5-10 minutes, and my vent switch whatever you wanna call it doesn't work either. I would like to have this fixed before winter. So far ive replaced a weathered line near the firewall but did not help. Thanks

 

check all the lines.. likely a leak somewhere.

trace it from the vacuum pump to along the cowl, and from there to the axle, etc.