I just installed TSM's disc conversion on my 14b SF. Skip @ TSM said I would not need any proportioning valves or residual valves since my 90 K5 has Rear anti lock brakes. The brakes work great as long as I'm in 2 wheel drive. No issues at all and I can stop great even runing 35's. The problem is when I shift into 4 Low or High I lose just about all of the rear brake. I do know that the Antil lock system is disengaged in 4 wheel. You would think I would have more brakes in the back with it disengaged. I thought about removing the antilock system but it ties into the VSS (Speedometer) and computer. Any advice?????