Fluid changes 10,000 miles ago. Was doing the same thing before and after fluid change. It is a 4L80 transmission.When was the last fluid/filter change? If not recent, consider one. Do you have the 4l80?
This was my the cause of my problem on my 93 C1500 with a 4L60e. I had hard, late shifts and a bit of idle fluctuations. Fuel pressure was marginal @ 10psi. Replaced fuel pump and got 13psi and hard shifts went away.. smooth again. I assume because I had to use more throttle than normal for given speed/condition the PCM thought I was trying to accelerate hard when I really wasn’t.Check your fuel pressure as well. The TPS tells the computer when to shift based on speed and throttle position
Thank you.Check your fuel pressure as well. The TPS tells the computer when to shift based on speed and throttle position