Engine - Vibration Complaints

Bulletin # P90-010

Section: PRODUCT

Date: 12/11/90

Applicable to: USA
CANADA

SUBJECT:
ENGINE/VEHICLE VIBRATION COMPLAINTS

An engine vibration or apparent driveline vibration that occurs under moderate to heavy acceleration between 55 - 60 mph (shortly after torque converter lock-up), may be due to an out of specification alternator mounting bracket, resulting in a mis-aligned alternator.

To verify this, first road test the vehicle to determine the vehicle speed, engine RPM and engine load where the vibration occurs. Then remove the alternator belt and re-test under the same driving conditions. If the vibration is now gone, proceed as follows:

Using a suitable straight-edge, approximately 12" long, place it across the power steering and alternator pulleys, holding the straight-edge flat against the face of the power steering pulley.

Measure the distance from the alternator pulley face to the straight-edge in 4 places, 90° apart (top, bottom and each side), at the outer-most edges.

If the pulley face is out of alignment more than 1/8" (3 mm) forward or rearward, or more than 1/16" (1.5 mm) top-to-bottom (nose-up or nose-down), the alternator bracket must be replaced.

Forward or rearward mis-alignment less than 1/8" (3 mm) can be corrected by installing washers (as shims) between the alternator and the bracket at the two lower mounting bolts.

A "nose-up" or "nose-down" condition, less than 1/16" (1.5 mm) may be considered normal, and no action need be taken.

Also, carefully examine the alternator belt for variation in cog width or apparent high or wide spots in the cord area.

Please contact RRNA Product Support at 1-800-562-5824 if you need further assistance.