1. Engine not tuned for peak RPM
    Tune the 2.5 / 3.3 or Pro .15 engine for performance.
  2. Slipper clutch is set too loose or is damaged
    Tighten or repair slipper clutch.
  3. Transmission shift hub requires adjustment
    Adjust the shift hub counterclockwise to lower the shift point (shift sooner) until the shift point is fine tuned. Refer to the owners manual for details on your model.  (If the vehicle was shifting into 2nd and it gradually stopped shifting, it is probably NOT a shift hub adjustment issue.  See items 1 and 2)
  4. 2-speed hub loose on shaft
    Tighten 2-speed hub onto shaft (Maxx trucks), or verify that the hub pin is present inside the shift hub. The hub must be securely fastened to the shaft.