i am have a problem with my four wheel drive seems the problem is with theeletric over vacuum switcheswhen in two wheel drive i have good vac to the lower switch when i go to 4 wheel drive i lose vac at the bottom and should have vac on the other with the gage in i can see the needle jump but go back to 0 it acts like it wants to open but gets stuck is this a common problem and is there a after market part


am i in the ballpark

 

2001 trooper with tod 3.5 auto