The NP 249 transfer case allows sport utility vehicles like the Jeep Grand Cherokee to switch between two-wheel drive and four-wheel drive. When not engaged, the transfer case delivers energy from the transmission only to the rear drive shaft. When engaged, it delivers energy to both the read drive shaft and the front drive shaft. Unlike other models that have a lever to engage four wheel drive, the NP 249 is a limited slip transfer case. When engaged it does not deliver energy to the front drive shaft unless it detects slippage from the rear tires.
Check fluid levels. Low levels or incorrect grade of lubricant result in a noisy transfer case in all gears. Dexron II Automatic Transmission fluid or an equivalent is required for the NP 249 transfer case.
Check shifter linkage. If the transfer case does not engage entirely in "4L" position, or jumps out of gear, the transfer case shifter linkage may be loose or binding. Check the shift fork for signs of cracks or wear.
Check output shaft seals and vent. Lubricants leaking from either one indicate the transfer case is overfilled with lubricants. The vent may be closed or blocked. Damaged or incorrectly installed output shaft seals cause leaks.
Test if the transfer case will shift into all ranges. Damaged internal gears or viscous coupler prevent the transfer case from shifting into "4-low" or "4-high" drives.
