Reading Comprehension- You need to get some. This thread is about brakes. Not the 4wd not working.
Do you understand how the brakes and the 4WD both operate using the SAME Vacuum system, that comment was a little uncalled for.
imcfarland93 has a valid point, if there is a vacuum leak between the transfer case and the front axle fork actuator, then only when he shifts into 4w would there be a vacuum leak, and he could be losing vacuum at the brake booster, might be something to double check!
Jeep 1:Used to have a 93 YJ 2.5l- 3.5" Black Diamond, Chevy TBI 5.7l V8, SM 465 4 speed, 8.8 rear( 4.10, L/S), rhinoline, Mile Marker 9000, NP 231, Had to sell it due to college
Jeep 2: 89/91 YJ, 4BT Cummins, NV4500, NP 231, Old Man Emu 2.5" suspension lift, 1" body lift.....Runs and drives, but very much a project
Interned at Novak Conversions 2 summers ago
Ask me about my 4BT Cummins Motor Mounts!!