Here's why:
* Popping sound: This points to something mechanically disengaging or binding within the transfer case.
* Stopping suddenly: The loss of drive suggests the transfer case is no longer transferring power to the axles.
* Resolving the issue by shifting to 4WD High or 2WD: This is a temporary fix; by engaging the 4WD system (even briefly), you might be re-aligning the failing components enough to get power back to the wheels. This highlights that the fault is likely within the transfer case, not the transmission.
Do NOT continue to drive the truck in this condition. Driving with a malfunctioning transfer case can cause significant additional damage:
* Chain damage: A failing chain can snap, severely damaging the transfer case's internals.
* Axle damage: Sudden loss of drive can stress the axles and drivetrain components.
* Further transmission damage: The transmission could be overloaded trying to compensate.
What you should do:
1. Stop driving the truck immediately.
2. Have the transfer case professionally inspected and repaired. This is not a DIY job for most people; the internal components of a transfer case are complex. A mechanic specializing in older trucks will be best equipped to diagnose the problem accurately and recommend the appropriate repair, whether it's a chain replacement, linkage adjustment, or a more extensive rebuild/replacement.
3. Avoid attempting to "fix" it by continually shifting into 4WD or 2WD. This is only a temporary workaround and risks further damage.
Ignoring this problem could lead to expensive repairs or even necessitate a transfer case replacement. Get it checked out by a mechanic as soon as possible.
