We replaced the Torque Converter on my 2008 Ford Explorer. My mechanic said that replacing it should take care of the shudddering between 45-50 Mph. Well it has not taken care of it and now the engine races when I start to take off after stopping at red light etc. HELP, I am getting very frustrated with my mechanic

Take it back, he needs to double check the fluid level, if it is full then either he put in the wrong stall speed converter or there is something wrong with the shift solenoids or control unit. Personally I would have tried the solenoids first due to the high failure rate they have.

Tennisshoes, Thank you for getting back to me. I took the car back to my mechanic. He checked the fluid level and it showed full. Still does the same thing. The other day I backed in a driveway that is pretty steep to unload some boxes. The car sat for about an hour and when I got in to leave and put it in drive the engine just raced and would not move, so I put in 3rd and it lurched forward a bit and the same, so I had to put in 1st to pull the car out of the driveway. That is when I took it in and he checked the fluid and it showed full. The car ran so much better before he put in the new torque converter. Do I have to take it back to him. The car is still under warranty until the first of the year. Could the new torque converter be bad?

That would be a reasonable conclusion, I would take it back.