I'm having a similar issue with my '98 3500 DRW. I also have RWAL. On every trip, the "BRAKE" and "ABS" lights come on after a couple miles. I guess I'll try flushing my fluid, too.
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'98 Ram 3500 - single cab DRW, 4WD, NV4500, 4.10s, No. 10 plate, 4K GSK, AFC springs, 4" exhaust, BHAF, Isspro gauges, 15.5° timing