Before anyone says there is no such thing as a stupid question, I should let you know that I have been a classroom teacher for 20 years and that I know for a fact that there is such a thing as a stupid question, so here's one for you. I have an E99 F250 with a ZF6. When I started it up to come to work yesterday morning, it cranked right over like it usually does. However, I had to leave in the middle of the day to take care of something and when I started it, it cranked over a little slow. It started with no problem and ran fine. About three hours later, I started it up again to go home and, again, it strained a little to turn over. On the way home, I stopped and got the batteries checked. One checked that it needed to be replaced and the other checked okay, so I only replaced one. My stupid question is, should I have replaced both batteries at the same time? After the I replaced the bad battery, it felt like the starter spun a little on start-up. Then this morning it felt like it was dragging again, so I'm thinking starter problems also. If I can get some good advice on this issue, I promise more stupid questions in the future.