Transfer Case Growl or Grinding Noise

	Cause	Correction
	DEFINITION: A faulty internal transfer case component that causes a low pitch growl or grinding noise in the transfer case while the vehicle is turning left or right or in a four wheel drive mode. A low pitch growl noise with the vehicle in 4LO or 4HI is to be considered normal. Heavy duty NQH transfer case applications are noisier by design in 4HI than are the light duty applications. 1. Compare the noise to a similar vehicle to see if a normal condition. 2. Identify the source of the noise using chassis ears and refer to the appropriate service manual section. 3. Note specifics such as when the noise is present (2HI, 4HI, OR 4LO). 4. Note if the noise relative to vehicle speed, is noisy on turns, or other specifics. 5. If the source of the noise is the transfer case, inspect for the correct fluid level. 6. Inspect the drain plug for large metal deposits. Small metal flakes and fine metal dust on the plug magnet are to be considered normal. Review the Symptoms - Transfer Case and perform the necessary inspections.
	Tire wear	Note: A growl noise that increases as vehicle speed increases may be caused by tires that are unevenly worn, unevenly inflated, or have an aggressive tread pattern. Rotate or substitute tires and retest. Tire and Wheel Inspection
	Propeller shaft center support bearing worn (as applicable)	Note: A growl or grinding noise that increases as vehicle speed increase may be caused by a worn center support bearing. Replace the center support bearing as required. Symptoms - Propeller Shaft
	Propeller shaft universal joints worn	Note: A growl or grinding noise that increases as vehicle speed increase may be caused by worn universal joints. Replace the universal joints as required. Symptoms - Propeller Shaft
	Front or rear axle bearings worn	Note: A growl or grinding noise that increases as vehicle speed increases may be caused by worn axle bearings. To determine if the noise is front axle related, remove the front propeller shaft and retest. Repair or replace the axle as required. Symptoms - Front Drive Axle or Symptoms - Rear Drive Axle
	Transmission rear output shaft bearing worn	Note: A growl or grinding noise that increases as transmission output shaft speed increases may be caused by a worn transmission output shaft bearing.

	Cause	Correction
		Replace transmission components as required. Symptoms - Automatic Transmission
	Transfer case fluid level low	Note: A growl or grinding noise that increases as transmission output shaft speed increases may be caused by a low transfer case fluid level. Fill the transfer case to the correct fluid level and retest.
	Transfer case input shaft bearing worn	Note: A high pitch whine or low pitch rumble noise that increases as transmission output shaft speed increases may be caused by a worn transfer case input shaft bearing. Replace the bearing as required. Transfer Case Disassemble and Transfer Case Assemble
	Transfer case front or rear output shaft bearings worn	Note: A high pitch whine or low pitch rumble noise that increases with road speed may be caused by the front or rear output shaft bearing. Replace the bearings as required. Transfer Case Disassemble and Transfer Case Assemble
	Transfer case shift fork pads broken or missing	Note: A growl, rattle, or grinding noise that occurs when a shift is commanded may be caused by broken or missing shift fork pads which may lead to incomplete engagement of the synchronizer teeth. High/Low Shift Components Cleaning and Inspection Replace the shift forks and pads as required. Transfer Case Disassemble and Transfer Case Assemble
	Transfer case range sleeve or input shaft gears worn	A growl or grinding noise that occurs when a shift is commanded may be caused by worn range sleeve gears and incomplete engagement. Repair or replace as required.
	Transfer case planetary carrier gears worn	Note: A high pitch whine or low pitch rumble noise that increases in 2HI only may be caused by worn or damaged planetary gears and ring gear damage. A whine noise that occurs in either 2HI or 4HI may be caused by worn planetary gear needle bearings or shafts. A high pitch whine that occurs in 4LO may be caused by worn planetary gears or annulus gear. Repair as required 1. Inspect for the following: Chipped, bent, or deformed teeth Planetary gear needle bearings worn Planetary gear thrust washers cracked or missing Seized or binding planetary gears High/Low Planetary Carrier Cleaning and Inspection

Cause	Correction
	2. Replace the planetary components as required.