Update : Put the auto trans switch in the middle (Eco - Mid- Power) and Took it out for a run after a cold start and it ran well, shifting happily all the way to OD. After 5km we stopped and put it in power mode and the old problem was back , i.e. didn't shift out of second. Then put it back in the mid position and even tried the eco mode but nothing changed. Wonder if this could be an electrical/electronic problem or wrong oil and just a coincidence that after 5km when we stopped the oil heated up and thinned out causing it not to shift out of 2nd. fyi, when we first started up the car, after the rebuild, we kept it idling for a while to ensure proper oil circulation, check for leaks etc hence when it ran the oil would have been hot. Im using CASTROL DEX III ATF