1988 GMC Sierra 5.7L 4WD Which alternator do I need? 85 amp? 100 amp? 105 amp?

Asked by Jun 18, 2015 at 08:04 PM about the GMC Sierra

Question type: Maintenance & Repair

I have easily determined which alternator for an '03 silverado by the service parts
identification codes in the glove box.  Not finding that for the GMC. Any suggestions?

2 Answers


Partsgeek.com has it,


The old alternator, if original, will have the amperage rating stamped on the outside of it (Example: 85A). If you can't find the stamp, or the alternator has been replaced before, usually vehicles with options such as air conditioning and rear window defogger had the higher amp alternator. HTH. -Jim

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