[mach66]

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

[classictruckman]

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

[GMAN]

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.