Asking here since I know some of you are familiar with this transmission. My son has a 2000 Z/28. Car has 200k miles on it and the 3-4 clutch pack finally took a dump. We swapped in another tranny that shifts wonderfully.......so long as you shift it manually. Put it in -D- and nothing happens. Put in 1st and it will accelerate just fine and will manually shift into 2nd and then drive. Come to a stop then you have to downshift to 1st and start the process again. Since I have all the gears I'm assuming it is not in 'limp-in' mode. It is not throwing any codes so I'm not really sure where to start checking. I'm guessing something electrical but not sure where to start. Any ideas? Thanks.