I have an 85 gs and need a new alternator. I'm looking to see if there's maybe a 3rd gen or just a first gen that would be an upgrade. Im open to maybe a new pulley too...depending on what affects it has. Street use only...not a race car

 

not 100% sure without searching "alternator upgrade", but i think the gsl-se alt is a slight upgrade to the 12a one and will be direct swap. the s4 may also be but i think the s5 requires some wiring mods to make it work, again not sure. those that have done any of these will chime in i'm sure.

 

I installed an S4 alternator on my '83. The wiring is the same, just plugs right in.

 

what years do the s4 span? 86-89?

and what kind of upgrade will this provide? Slightly more current to the battery?

 

10+amp upgrade i believe.

S4 span from 86-88.

S5 has 10 more amps than the s4 but you will have to do a little wiring.

 

Thanks for the tip. I want to keep the same wiring if possibly, so I may go with the s4 alternator. Pulley is the same i take it? Along with mounting points?

 

Mounting points are the same. I THINK the pullys are the same. My buddy has a 81, he needed a alternator so i sold him a S4 alt. Im almost positive he didnt change the pully off the s4 alt. That was a year ago so i cant recall.

 

This has been covered many times before. Fc and FD alternators are upgrades and one guy put in a GM alt. Search and use the archives.

S4 wiring and pulley are same.