Vibration Highway Speed Z71 and Z85 Suspension - keywords balance rough shake speed tire wheel wobble

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Customers with the Z71 or Z85 suspension package may experience a vibration while driving, usually at highway speeds.

Important: Please review bulletin 03-00-91-001B.

Engineering is currently testing redesigned tires. At this time, the correct procedure is to replace the tires with the same brand and model.

In production, Z71 vehicles, equipped with P265/75R15 General tires, built after 8/2/04 have updated tires installed. To obtain an updated tire(s) (P265/75R15 only) for a service application, inspect the last 4 numbers of the DOT code. Tires manufactured with date code 2504 (25th week of 2004) or higher, will be an updated tire. When ordering the tire(s), it is important to order the tire(s) by its article number from the tire manufacturer or store. The article number is the manufacturer's part number. Order article number 1548080 to obtain the P265/75R15 tire(s) with date code 2504 or higher. Tires ordered by this article number will assure the correct tire(s) will be received. When replacing and balancing these tires, typical road force variations should be 20 lbs or less for the P265 series tire. After this road force is accomplished, test drive to confirm vibration has been eliminated.

Updated P235/75R15 tires are now available. In production, Z85 vehicles, equipped with P235/75R15 General tires, built in the 2006 model year have these updated tires. To obtain an updated tire(s) (P235/75R15 only) for a service application, inspect the last 4 numbers of the DOT code. Tires manufactured with date code 2105 (21st week of 2005) or higher, will be an updated tire. When ordering the tire(s), it is important to order the tire(s) by its article number from the tire manufacturer or store. The article number is the manufacturer's part number. Order article number 1548240 to obtain the P235/75R15 tire(s) with date code 2105 or higher. Tires ordered by this article number will assure the correct tire(s) will be received. When replacing and balancing these tires, typical road force variations should be 17 lbs or less for the P235 series tire. After this road force is accomplished, test drive to confirm vibration has been eliminated.

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.