robuga

Ok I changed the fluids and filter on the automatic tranny ,it started slipping when drove over ten miles like it was over heating,So i changed the fluids and filter and now it pulls good no slippage but want engage in 1 st gear or overdrive.I even tried to manuely put it in first and still want engage.So I heard i probably damaged the shifting sensors.When I removed the pan I had a rough time removing the pan and had to get jack and jack back of tranny up so i could remove pan to change filter and refill fluids and it pulled good just no 1st or OD.SO i jacked up tranny again and drained fluids and checked the shift sensors and removed them to check them real good but showed no signs of them being damaged and ohmed them out and they showed contiunity,so i put them back in and still the problem is the same,NO 1st or over drive and when u come to a stop you have to take off in 2nd or 3rd and when it shifts from 2nd to 3rd it shifts hard.Will they be signs of breakage or cracked on the shift sensors if I did damaged them?Plz help need my truck back? Of yeah I put the Auto Zone ATF Dex/merc