05 Yukon XL, 288k miles. Extremely slow acceleration from a stop, but as first gets the engine to higher RPM, it has plenty of get up and go, no issues with 2nd, 3rd, or 4th. I have it scheduled for an ATF change, hoping that might help. Hoping to get an idea of why it moves so slow off the line. Even putting my foot to the floor yields granny acceleration.