The pulley you guys got are for a n/a 5.4 which is also 8-rib but the alternator pulley has a different offset and smaller diameter on those trucks. The Lightning trucks have their own specific alternator pulley. I was never able to find the correct part # though

 

Cant you just switch the pully from your original stock unit?

 

I'm thinking the only thing which was done to the alternator was install a different size pulley to start out with. I seriously doubt that there are any changes to the internals. When the alternator spins faster due to the smaller pulley it generates more amps. So if I installed the stock size pulley I don't think the alternator would generate any more amps than a stock one.

 

Alt amp output is directly related to the amount of windings inside. Putting on a smaller pulley isnt going to get you anymore amperage or voltage.

Pull it apart and see how much more windings the higher amp rated one has compared to the stock one.

HIGH VOLTAGE

 

I have heard in the past when people install underdrive crank pullies on their cars that it can mess up the electric system. If one spins their alternator slower do they get less amps?
Also at an idle with my stock alternator my lights dim. When I rev the engine(spin the alternator faster) the lights don't dim...


LOW VOLTAGE

 

Let me repeat,

The only thing the determines TOTAL alt amperage output is the amount of windings. Obviously when you spin an alt slower, its output will be lower also, but spinning a stock alt faster wont yeild you anymore amps than what its already built for.

By the way, they arent considered alternators anymore, they are once again being called generators.

Most likely your stock alt was bad to begin with, did you have it tested?

NEW TREND

 

I had it tested. They said it was still good. I have a lot of electronics hooked up like e fan, stereo amp, gauges, intercooler fans, gauges, etc.