Re: Automatic Transmission "slipping"
Hmm usually the d4 light flashes when the tranny has a problem. The sport light should only be used when on the highway/freeway; it just lets the car rev up higher I remember, maybe there's a lose wire somewhere or he's accidentally hitting it without knowing. My old '90 slipped all the time from 1st to second but it held up fine. I suggest changing the transmission fluid with gm synchromesh. As far as parts, go to a local junkyard/wrecker and see what's available. Good luck.