Hello,
I have a 2006 International 7400-DT466. It's a 6wheel dump and it quit running yesterday. Now it won't even turn over. It has brand new batteries that are 3 weeks old.
The diff. lock light is now flashing and it's never done this before.
Any ideas where to start?
Thanks in advance-Chris

 

Check for a burnt fuse holder on top of the batteries, we had a 4300 series which would burn that fuse holder every couple months, also had a 4200 that burnt every connector on that same wire which runs from the batteries to the ECM

 

Check all connections around batteries. Sometimes corrosion can build up and interfere with the connection. You might just have a wire that is a little loose. Over the years I have had battery cables that have vibrated loose over time and the starter would not even click. Only a couple of years ago, I had a small connector to break and lose connection at the solenoid. I replaced the connector and have not had a problem since. The connector was difficult to spot. From your post, I think it is probably something very simple and has to do with the wiring.