2001 Ford F-150

Transmission problem
2001 Ford F150 V8 Automatic 100000 miles

I had to replace my motor this past year. The freeze plugs blew out 3 separate times in 2 years. I replaced the moter with a used one that had 75000 miles on it. Since I got it back the overdrive has ony gone into overdrive 3 times in 3000 miles. Now the service engine soon light has gone on. I had a manual hand held scanner reset the service light and it went off. About 50 miles later it went back on. Any ideas?
July 5, 2008.

You should get the codes as it will help pin point the troubled area
post them for more help

Jul 5, 2008.