I have an 1998 Ford F-150 Lariat and I am having what seems like transmission problems. I just recently replaced the transmission, but now the speedometer is off by 50mph and it won't shift properly. When it does shift, it shifts really hard. It also feels like there is no power to the truck at all. I know it cannot be the transmission due to it only having 40,000 miles on it. Let me know what you think the problem is, thanks!