1992 GMC Safari Q&A
1992 GMC Safari Question: What causes my wheels to not be able to roll when I put in drive?
If it is like this ALL the time even without engine running and brakes never release with NO pedal travel, suspect blockage in the brake fluid circuits, fluid cant return! Most likely the master cylinder needs to be replaced and system flushed. Fluid dirty, black in color? Have it checked out by a mechanic, not a diy repair, or do you know someone that is pretty car savvy and will help you out with some testing? - pushrod
could be brk booster issues or hydraboost depending on how veh is equipped - globalhelper