Nissan Repair: Autobox problem, nissan largo, torque converter

Question
Hi,

I have a nissan largo 1996 2ltr TD with an automatic box, the problem is the high gear. it does not want to work when cold it will only engage after about 20 mins of driving.
Please can you help me.
I am not sure when or if the autobox oil has been changed,  I have had the car for about 10mth this problem develeped about 6 weeks ago.

Have tried to find a manual but with no luck.

Many Thanks

Dave

Answer
Dave,

Overdrive is controlled through a variety of sensors.  One is the temperature sensor that will not allow the overdrive or lock up torque converter to lock until the vehicle is at operating temperature.  Make sure that the thermostat is not stuck open and the vehicle does get to operating temperature.  If it is at operating temperature replace the temperature sensor that sends the signal to the computer for the transmission reading.