GMC Troubleshooting Questions? Ask a Mechanic for Answers
Hi there, I am Cam. Can I get your first name please?With your transmission, what is the exact colour and condition of the transmission fluid? You say it needs to be changed, but if its really brown then a change may not be enough.I have a suspicion it’s the torque converter clutch causing it, but we can explore that.
OK Max, that does lead me to think that either you torque converter clutch is slipping or you have just general wear in the transmission. A hard shift is simply the increase of line pressure inside the transmission. With your transmission fluid showing it not Brown, I believe the next best course of action to replace the filter and replace all the fluid. If that doesn't change the shifting, then perhaps we have a feeling pressure control solenoid inside the transmission. It might be cheap enough to consider replacing while you have the pen off. The gasket is reusable provided it's not damaged.