the transmission made a light clunk noise and it lost 1st gear. engine code came up on my scanner p0750 shift solenoid A circuit. i dropped the pan and valve body and put new shift solenoid box on . 1st gear came back went through gears tyhe first several takeoffs . when it got warmed up it lost 2nd gear and o.d.and lightn came back on ,code came up p0841 low range pressureswitch sense circuit is that pressure switch in thye same piece i installed , did i get a defective part ? any advice would be much appreciated

 

Looks to be a separate sensor. (assuming 5.7 engine.....) I suspect it is inside the pan on your trans.

 

Passenger side of trans above pan on the outside there is a Govenor Pressure Transducer solenoid which controls pressure. Change that with one from dealer not aftermarket probably about $70 . The pack you changed inside is the solenoid Pack which has every other solenoid on it. Keep your original solenoid pack probably wasn't any thing wrong with it.