Skip the auto shop - Our mechanics make house calls

Q: Engine revved in drive - 2006 Chevrolet Avalanche 2500

asked by on

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?

A: This sounds like the transfer case isn'...

This sounds like the transfer case isn't completely engaging selected gears (High/Low, 2/4wheel drive). There is a GM Service Bulletin on this issue - TSB Reference #3424. Check with your dealer on this one.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Transfer case not fully engaging in low

The transfer case lock switch may be the cause of the transfer case not getting full engagement. The manufacturer has a technical bulletin to check the system by loosening the switch up and inspecting engagement, then, if okay, to replace...

Q: would a bad oxygen sensor keep my truck from starting?

The O2 sensor will not cause the no start. The no start can be caused by the fuel pump or the ignition system. You should check the engine for spark and fuel pressure, when it is not turning on to...

Q: Car not going from park into reverse

Hi. There is a solenoid near your shifter that releases the shifter when the brake is applied. This circuit will need to be tested to determine if the brake switch, wiring, or solenoid is faulty. If you need further assistance,...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.