1997 GMC Suburban electrical system problems

While driving the suburban just shuts off without warning, this happens on flat roads as well as hilly roads, the dealer was not able to duplicate the problem, but the entire computer ignition and the alternator were replaced. However, the truck continues to do the same thing.

1997 GMC suburban- multiple engine & transmission failures. At 60,000 miles, vehicle began to shift hard. Returned to shop for diagnosis and repairs several times for work. Finally, while driving the vehicle in city traffic, the transmission failed compeletly. Required valve cover and transmission rebuild @ cost of $2,000. On december 27 '03, had to replace the radiator. On jan 17 '04, discovered that there was no antifreeze in new radiator. Returned to mechanic who replaced the radiator.