My 2500 2wd automatic disengages overdrive at highway speeds (55-75mph) intermittenly. Problem evently would not allow transmission to go into o/d. Transmition shop checked the TSB's and replaced PCM, TCP and main computer which seemed to solve the problem for about a year ($1300). The problem has resurfaced (intermittenly of course). I am looking for the cause? Has any one else with the same truck experienced this problem?