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This page is taken directly from our digital online manual 24066 for the 1999-2006 Chevrolet Silverado/GMC Sierra 1500, 2500, and 3500 pickup trucks (including 2007 Silverado Classics and Sierra Classics) and Chevy Avalanche, Tahoe, and Suburban, and GMC Yukon SUVs, 2WD or 4WD with gasoline engines. We recommend you check the auxiliary drive belt, and on V8 motors the second AC compressor belt, every 6,000 miles or 6 months, whichever comes first, and replace it when it shows signs of wear. These engines use spring loaded automatic tensioners, so no adjustment is needed. Under normal use, the alternator itself will likely last well over 100,000 miles.
Auxiliary Drive Belt Removal and Alternator Replacement
This video is specifically for the 4.8L, 5.3L and 6.0L V8 engines, but the 4.3L V6 is similar.
Note: On models equipped with Theftlock audio system be sure the lockout feature is turned off before disconnecting the battery. Instructions for deactivation are in section 5 of the General Information chapter of the Haynes manual, or in the vehicle owner's manual.
- Disconnect the cable from the negative battery terminal.
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Remove the drivebelt by rotating the spring loaded tensioner with a wrench, and slipping the belt off the pulleys (see Chapter 1 of your Haynes manual for details).
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(See illustration) Disconnect the output wire and the electrical connector from the alternator.
Remove the nut and wire terminal from the output terminal (A) and disconnect the alternator electrical connector (B)
On V6 models, also remove the bracket bolt (if equipped) at the rear of the alternator (arrow)
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If you are replacing the alternator, it can be helpful to take the old one with you when purchasing a replacement unit. Make sure the new/rebuilt unit looks identical to the old alternator with the mounting bolts in the same location. Look at the terminals - they should be the same in number, size and location as on the old alternator. Finally, look at the identification numbers - they will be stamped into the housing. Make sure the numbers are the same on both alternators.
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Some new/rebuilt alternators do not have a pulley installed, so you may have to switch the pulley from the old unit to the new/rebuilt one. When buying an alternator, find out the shop’s policy regarding pulleys; some shops will perform this service free of charge.
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Installation is the reverse of removal. Tighten the mounting bolts to the proper torque:
Front mounting bolts 37 ft-lbs
Rear bracket bolt (V6)
1999-2001 18 ft-lbs
2002-2007 30 ft-lbs -
Reinstall the drivebelt.
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Check the charging voltage to verify proper operation of the alternator. WIth the engine running it should be more than 12.5 volts, but less than 14.7.