On the 4L80-E Transmission (Diesel and 7.4L gas engine), Transmission fluid may leak through the electrical connector on the side of the transmission, damaging the wire harness and causing the transmission to shift erratically. Our technicians tell us there are updated shift solenoids, an internal transmission harness, and a connector pigtail available to correct this fault.
Transmission fluid leaking, erratic shifting on GMC Suburban 2500
Average mileage: 176,000 (176,000–176,000)
Drive Train affected: 4WD
3 people reported this problem
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The transmission only shifts past 2nd sometimes. We took it and had the codes pulled and they came back with TCC error, TCS circuit, trans code low gear ratio and trans code high gear ratio. We took it to a tranny shop and they drove it and looked it over and said it was in pretty good shape for a 94 with 176000 miles on it. Of course while they drove it the truck shifted fine. So now we are stuck trying to figure out exactly what is wrong and how to fix it.