Q: Engine revved in drive - 2006 Chevrolet Avalanche 2500

asked by on September 04, 2016

My truck’s engine revved freely when the transmission was in Drive, as if it were in Neutral. On the shoulder of the road, I coasted to a stop, then shifted into Park, and released the brake pedal. At that point, my truck started rolling forward, downhill, I assume because the transfer case shifted into neutral. The indicator was not on. I turned off the engine. I had a code reader, but it did not show any codes at all.

I restarted the engine and shifted into Drive, at which time I felt the transmission engage (the transfer case must have engaged from neutral). Gradually I accelerated and then drove down the highway for ¼ mile. When I released the accelerator pedal, the transfer case shifted into neutral again, engine revving when it was still in Drive. After I coasted to a stop on the shoulder, I pressed the 4WD high and then felt the transfer case engage, pressed 2WD hi and felt the transfer case disengaged; however, now it was in 2WD instead of neutral.

Gradually accelerating I drove down the highway and when I released the gas pedal the transfer case shifted into neutral again while the engine was revving with the truck in Drive. Coasted to a stop again and repeated the sequence. Shifted into 3rd, gradually accelerated, and drove some more and the transfer case remained in 2WD high. On the shoulder I stopped slowly, turned off the truck, restarted, and shifted into Drive, gradually accelerated and drove some more - released pedal and transfer case shifted once again into neutral. In your assessment, what is causing this problem and what do I do to correct it?

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