I was having a problem with my o/d light flashing and my truck would kick out of over drive. So I replaced the speed sensor control and it ran fine for about two weeks. Then one day I went to the store and it would not go above 30mph. I was told it is in limp mode and have replaced the "TPC" sensor, the mass air intake sensor and replaced the O2 sensor and none of these have seemed to fix it. Please help!
First of all, you need to find out the code in the trans system it sounds like you have guessed up to this point hoping for a resolution.
Once the code is pulled, the failure will have to be traced down to find out the real solution to the problem.