If you are new to repairs, have a trusted transmission shop diagnose and replace the output speed sensor rather than attempting it yourself. A failed sensor can put the transmission in limp mode and prevent upshifts. To learn, buy a vehicle-specific Haynes manual and start with basic maintenance before tackling sensors, since the correct sensor must be identified.
The owner of a 1999 Jeep Grand Cherokee Laredo asked where the transmission is and whether to replace the output speed sensor personally or pay a shop. An expert advised a shop because the owner was unfamiliar with the vehicle, noted that speed sensors can be easy or difficult and that the correct one must be identified, and recommended a service manual plus basic maintenance first. The owner later said another shop blamed the output speed sensor, but the shifting problem cleared after refueling, and asked about other causes of no upshift. The expert explained that a sensor fault can force limp mode and prevent higher-gear shifts until repaired. Another reply recommended a Haynes manual and said the repair should not be difficult if researched first.
