Why does my truck not shift into 4th gear

Hello, the P0446 code has to do with an evaporative emissions systems concern. This has nothing to do with the transmission operation as you have described it. What testing was performed to determine that you needed to replace shift solenoids? If there are no diagnostic trouble codes present relating to engine or transmission performance, then there are likely no electronic concerns present. I respect the fact that you need the truck and that it's quite concerning that there has been a failure. But nothing will replace the ability to diagnose and inspect the vehicle from a professional point of you so that you can get the real information on what it will take to repair your vehicle. What good is it to spend hundreds of dollars on parts that might not be necessary? Sometimes the professionals are necessary to find out what's going on. Once armed with valid and valuable information, you can then decide how to proceed with repairs. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops