My original gearbox always seemed to change up at lower revs than I expected and was reluctant to drop down a gear when climbing a hill for instance, I had to give it plenty of throttle to make it change down. The Ascot, a 4.6 GEMS, changed up at slightly higher revs (around 2,000 rpm compared with 1,700 on my original box) and would drop down a gear far more readily when needed. My car now drives much the same as the 4.6 (if not better) although I don't know if this is a difference between the two gearboxes and torque converters, my original box had been on its last legs since I've owned the car or if the fact I am now running a 4.6 gearbox ECU and the original one had been re-programmed to meet the requirements of the original owners (Greater Manchester Police) I have no idea. The larger torque converter means I now have effectively a heavier flywheel so I thought that might make it feel different, but it doesn't seem to have done.
The gearbox supplier has fitted the 4.6 gearbox to over 30 4.0 litre cars over the years and has always left the original 4.0 litre ECU in place. I suspect the only difference is the range over which adjustments to suit driving conditions can move. I will admit that mine is now so smooth when accelerating with the rev counter just hopping between 2,000 and 2,200 rpm as it goes up through the gears but the changes can't be felt at all.
Going back to the original subject, I'm about to go out in mine and it is already up to over 26 degrees outside, so I'm going to monitor the engine temperature and see what it is running at now.