2014 Lariat 5.0 with 35" tires. 13,000 miles. During low to moderate acceleration when the trans hits 3rd gear and is about half way to up shifting to 4th, the RPM's drop about 2 hundred, then come back up. The truck continues to accelerate and it shifts into 4th. No problems with any other up shifts and if I get on it hard the rpm drop does not happen. Either that or I just don't see or feel it. When Tow/Haul is on it does not do it. I have made sure I am not moving my foot. You can actually see the tach drop, then come back up, then it shifts into fourth. Any suggestions?

 

Do nothing. It's the torque converter locking. That's the way it is supposed to work.

 

I thought that is what it might be, but why is it locking so quick especially at low speeds and only in 3rd gear? It's really annoying sometimes.

 

Gas mileage.