stantonbox

[size=7]It's winter and I'm using my 4WD. There's a definite whine sound that can be heard from the front differential area. It also growls when certain road surfaces are encountered. I'm driving a 2001 Tahoe with 84k miles. AT 5,000 miles, the dealer overhauled the front differential under warranty as the bearings were wiped out. Is this sound normal and nothing to be concerned about?

John86

Condition/Concern:
Groan, growl, or moan coming from the vehicle when operating the vehicle in four wheel drive.
Recommendation/Instructions:
The vibration that is heard or felt is a result of the front axle being excited to resonance at its natural frequency. This is a combination of: the transfer case chain link frequency, engine firing frequency, tire circumference variation, and various other tolerances built into the 4WD system.
ADDITIONAL NOTE #1:
A groan, growl or moan noise on deceleration while in 4WD is also the result of loading the transfer case chain which is an operating characteristic. This is just one example of a transfer case link frequency as noted above.
ADDITIONAL NOTE #2:
On certain models, such as 3/4 and 1 ton vehicle, tire pressures can vary from front to rear based on the manufacturer's specifications. As an example the manufacturer's specifications for tire pressures on a 03 K2500 Suburban are front: 50 PSI, rear: 80 PSI.
The difference in tire pressures affects the rolling tire circumference from front to rear which can increase driveline noise while in 4WD which is an operating characteristic.
For test purposes, drop the tire pressure in the rear to match the front. If the noise is reduced or eliminated this confirms the difference in tire pressures from front to rear can affect the noise when operated in 4WD. Set the rear tire pressure back to the manufacturer's specification. For vehicles with same tire pressures front to rear, swap tires from an identically built vehicle that does not seem to exhibit the concern and re-evaluate both vehicles.
No repairs are recommended for this condition.
For more information regarding driveline noises while in four wheel drive refer to the latest version of TSB 01-04-18-001D.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.