i've noticed that at around 4000 rpm or so right before i shift into a higher gear my alternator gauge dips down a little bit....not enough to worry me, but enough to catch my attention.....as soon as it shifts and the rpms drop it goes back up to the normal spot....is that a normal thing for these cars, are the alternators only rated to around 4000 rpm or something....just looking for a few ideas before i start to get worried

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88 Trans Am, 5.0L TPI, flowmaster cat back, high flow cat, WS-6 performance suspension, black w/ t-tops, automatic transmission....soon to be armed w/ a 5.7 TPI

 

Check the tension on your alternator belt. Probably starting to slip at the higher RPM resulting in the dip. I would just replace the belt anticipating glazing.

 

i was thinking that, but it's a serpentine and nothing else lost power....but maybe you're right...i hope so

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88 Trans Am, 5.0L TPI, flowmaster cat back, high flow cat, WS-6 performance suspension, black w/ t-tops, automatic transmission....soon to be armed w/ a 5.7 TPI

 

Knowing its a serpentine helps the diagnosis. At the higher RPM the belt heats up and stretches. Not to mention the centriputal force placed on the belt. Check your tensioner indicators with the car running. If they are anywhere close to being out of limits replace the belt. The alternator has the smallest rotational field (pulley size) and reacts quicker to the slippage than other pulleys do. Less contact area between the pulley and the belt. You see a noticeable difference because the alternator has a direct reading to you via the voltage meter. You may also notice a ratcheting in the power steering due to slippage on the power steering pump. Hope this helps.