The car has been in two shops so far. The first shop installed a new valve body that cost $1200 and did not fix the problem. The second shop has taken the transmission out and disassembled it and can only find some worn clutches. They now are telling me to put in another used transmission that they will supply but if it does not fix the problem I must pay for the labor to tear it down again and they will pay for the parts. I cannot get anyone yet who knows what to fix in this transmission. Here is what it is doing

1,2,3 gears work fine in all modes. When in (D) the trans will shift from 3 to 4 and the motor revs but nothing. The car slows down and then drops back into 3. In manual mode I can shift from 1 thru 6 but only 1,2&3 work. 4,5&6 just give motor revs. None of this ever makes the transmission throw a code. Any idea