I have a 91 Chevy dually with a tbi 454 and auto 4L80. When I got the truck the guy told me at times the chip in the ECM gets lose and the trans will shift funny. I drove it for over a year before I had a problem. I was driving one day hulling a trailer loaded and I hit a bump. The truck downshifted and engine light came on. Trans acted like it was In default. Shifting vary hard and high in the rps's. When I got home I removed the chip. It's a jet prom chip. I plugged it back In and drove it for a few more months. It happened two more times. Last time I took a work glove and shoved it in there and zip tied it together lol. Had no problems. Now what's happing is the truck has a Random misfire at times. Did a full tuneup and same problem. The trans is acting funny too. It will hunt for a gear like at 45 mph. It was downshift then shift back a lot. Same on the highway. Trans oil is clean and topped off. Trans has only 20k on it and it's a gm certafit trans. I feel my ECM or the chip is going. I know the chips are burnt for my specific setup so were can I get a stock chip? I ready don't care for this setup because the trans shifts hard. Sorry for the long story lol. Thanks for any info.
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