4WD Models with Noise, Vibration on Dry Pavement - keywords 04-04-18-001D 226 233E 236 241 243E 246 246EAU axle bearing bind case chatter chuggle decelerate differential front grab high HI4
| Subject: | 4WD Models With Noise, Vibration On Dry Pavement |
| Models: | 1996-2007 Light Duty Trucks and Utilities |
| Equipped with 4WD |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
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.
