If your 4WD system has been overloaded or neglected, you may be experiencing issues with your 4x4. Here are common scenarios when dealing with 4-wheel drive problems and how to fix them.
Inaccurate 4WD Indicator
When the four wheel drive fails to engage but the light on the dash says that it has - or the light isn’t on when 4WD is engaged - you've got an "inaccurate indicator," and that's a frustrating problem.
* First, determine if the four wheel drive is engaging properly. This can be tricky (see notes below).
*If the light doesn’t come on when the 4WD truly is engaged, the bulb likely needs to be replaced.
*If the light stays on even when the 4WD system is off, the problem is almost certainly the switch.
NOTE: If you're trying to determine if your vehicle's 4WD is working, you may have some trouble. The best way to see if the system is working is to put the vehicle on a lift. If that's not possible, you can try the following trick.
Find a dry parking lot with smooth paving, then engage the 4WD. Start driving forward slowly (just a couple of MPH) and turn the steering wheel as hard as you can to the right or left. If you feel your vehicle "hop" or stutter, straighten the steering wheel and it should go away. This hopping/stuttering is proof that the 4WD system is engaging.
The problem with this "trick" is that a) it doesn't work for vehicles with AWD (rather than 4WD), and b) it's not always easy to feel the "hop" in 4-HI. Still, it's worth a shot.
4WD is Stuck On
Some Chevys, especially older models, might get stuck in 4WD mode. When this happens, the indicator light will usually start to flash. Cutting off the engine is one way to disengage the four wheel drive. To fix the problem, try putting the vehicle in reverse and drive backwards for about the length of your SUV or truck. Put it back into drive and the 4WD should now be disengaged. If it still isn’t, put the 4-wheel drive lever in low mode and move it to two wheel mode before shutting it off. Should the problem persist, it may be an issue with the transmission and it may be time to consult a Chevy mechanic.
4WD Slips into Neutral
Your Chevy’s transfer shifter fork is what allows for the shift between normal drive and 4WD mode. It can break over time and lead to the vehicle slipping from 4WD to neutral. If this happens, you simply need to replace the transfer shift fork.
For further diagnosis, please consult a certified GM mechanic when the problem can’t be identified with this advice. There are many unrelated component problems that may mimic four drive problems, such as sticking calipers, a slipping transmission, and a slew of other issues.