I have a 1989 4.0 and ever since I owned the truck my alternator quits more than it should.
I bought it with 32000 miles and had my first alternator professionally re-built at around 38000 miles.
Then it went again at 63000 miles and had it re-built again.
Now at 71000 I am getting a very weak voltage signal. Sometimes at random incidences the voltage gauge will spike up to ~13 like it is charging like normal but will then go back down to ~10 after a short amount of time. It mostly stays at around ~10 volts now. Why does this alternator die so often? or is this normal....? To fix this issue I am thinking of getting an alternator from ac/delco or a stronger built one that puts out 100 amps.