P2723 CEL CODE what do i fix

[stang0303]

Replaced with new tehcm. Still did not fix issues. Car will barely move then check engine light comes on and it seems to work in 4th gear only. I can drive hwy speeds no problem. Slow starts since its in 4th gear. Im thinking it needs trans rebuild now. Weird thing is no metal shavings in fluid. And if it was a pump issue wpuld 4th through 6th gear not work? The fluid i did pull put after just replacing it was dark grey and black when i put it in see thru container. Clutches? I was hoping not to spend $3000 on a rebuild. Any other suggestions?