Skip the auto shop - Our mechanics make house calls

Q: 4WD is not engaging on my1997 Chevy Blazer

asked by on

I recently discovered that my 4wd has stopped functioning. I have replaced both the actuator under the battery tray and the actuator valve on the transfer case and is still non-functional. I can hear the transfer case switching to 4hi and 4lo but it does not lock the front differential. What is weird though is if I want to go over a curb, I can put in in 4lo and I can feel the front wheels pull the truck over the curb. But if the rear wheels spin, it immediately disengages. I tried to get out of a muddy field and I put it in 4hi then 4lo but only the rear wheels were spinning. I don't know what else to check. I really need the 4wd since I live in a snowy region. Any help is appreciated.

My car has 98000 miles.
My car has an automatic transmission.

A: Hi there. The problem with the transfer cas...

Hi there. The problem with the transfer case can be caused by the encoder motor/transfer case motor loosing power, the transfer case engagement switch failing or loosing power, the vacuum actuator under battery tray loosing vacuum, the vacuum actuator valve leaking vacuum on the transfer case, or a broken cable from actuator to front differential.

Since you replaced the actuator under the battery and the actuator valve on the transfer case, then the problem lies within the motor on the transfer case, the transfer case engagement switch in the cab, or the cable that runs from the actuator to the front differential. Check the switch in the cab to make sure that it has power and is keeping power while in 4x4 mode. If there is power and the switch is okay, then check the motor on the transfer case to see if it is coming on.

Check for power on the harness to the motor and ground to the harness. If the harness is good and there is power and ground but the motor is not working, then replace the motor. If the motor is working, then you need to replace the cable to the front axles so it can engage and lock the front axle. If the cable is working fine, then you may need to have your transfer case rebuilt or replaced (if all options are exhausted). If you need further assistance diagnosing your transfer case, then seek out a professional, such as one from YourMechanic, to help you with your vehicle.

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・Fair and transparent pricing

Get a quote

What others are asking

Q: will start after jumpstart and then wont idle

If your engine will not run after being jump-started and the cables are disconnected, I would recommend ensuring that the connections to your alternator are good. If the alternator is not connected properly or is faulty, this could cause the...

Q: Trouble starting in the mornings.

Hi There, It sounds like you may have something causing an intermittent problem prohibiting the motor to start. Things like this are commonly related to starters, batteries, starter relays, etc. It sounds like you have had these items checked with...

Q: Will a 95 RWD transmission be compatible with a 94 4x4, both F-150.

Hi there. The transmission in your truck is called an AODE or 4R70E. This type of transmission did not change year of design until 1998. From the year 1993 to 1997, the transmission was the same. The only difference was...

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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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...