ok i was wheeling today went thu sand got i had it engauged i 4wd looked at the tires saw they werent spining i just did a front axel u joint replacement a few days ago i think it might be my vac line the front driveshaft spins but not the tire any ideas if the vac line are bad were can i get new ones

 

I just had similar troubles where the vacuum line came disconnected from the rear of the axle. For me it was as simple as reattaching the line.

 

Check your vacuum lines and make sure they're all connected, especially at the axle. Make sure they have slack in the lines to travel with the suspension. I had mine disconnect before because the po zip tied the lines to keep them from getting hung up but didnt give enough slack to travel. Also check the axle fork actuator for leaks. I don't think you can buy the vacuum lines brand new from anywhere. I got mine from an xj at the junkyard. Any 87 to 90 xj with the np 231 will have the vacuum harness