I went to the beach Sunday with the intent of driving out on the sand. The 4wd would not engage, no lights on the dash, no clicks, no clunks, in either 4H or 4L. While driving 35mph coming back, I turned the switch to 4H and heard gears grinding and quickly turned the switch back to 2WD. When I got home sitting in the driveway, 4H and 4L appeared to work with the dash lights indicating so and I heard the clunk when it engaged 4L.
Any ideas on what I can do to avoid this happening again? It engaged again every time I've tried it since then. Once before 2 or 3 years ago, it failed to engage at the beach and then has worked fine ever since.