have NIssan Pathfinder Car 2003 model with VQ35 engine.
The vehicle uses Automatic Transmission system. However, the vehicle gear system automatically changes from 1 to 2 to 3 in Drive mode. When the vehicle attends to the speed of 60km/hr, the automatic gear system does not change from 3 to 4 and soon-on.
I checked the transmission oil, the level is ok. I have changed the gear box and still the same problem persists.
Please advice me on What to do?
Sounds like it may be in your best interest to have a transmission shop scan the computer for possible stored codes. This would be the best first course of action.
When you replaced the transmission did you also replace the VSS – Vehicle Speed Sensor and torque converter?