Rebuilding an 03 f4i for my son. Got it all together except for the plastics (waiting on those to show up). Runs great, idles great, andsounds great. Took for a test drive and once I get to 25mph in second gear, it shifts into neutral by itself. First I thought I must have hit it with my foot. But over and over at 25mph it shifts to neutral from 2nd gear. Now I can shift it back into 2nd and keep going and shift all the way through the gears and no other problems. I have know idea what the heck is going on. I did have to replace the shift linkage, but how can you mess up putting that on? Just changed the oil in it, but it hasn't been run for a few years. Should I change it again? Could I have messed up the shift linkage? Any ideas would be greatly appreciated.