I have an 96 GMC with a 5.7l auto. When hwy driving if I kick into passing gear my amps start droping quickly, the headlights dim, the gauge can get down to 8-9 amps if it stays in passing gear long enough. The truck runs fine otherwise other then hard starting in the morning at times. I don't think its the alternater because the the truck charges fine runs around 14 amps when driving. Is there somthing in the tranny that wound suck amps in passing gear? Maybe something in the ignition when the engine revs up that high. Anyone else have the same problem? Any ideas?