Tomcat588

My brother an I currently own a couple of 2005 CX613's that were formerly Air Product fleet trucks. From what I can tell they have been well maintained through their career at AP. The trucks came to us with 450K and 550K on the odometers. We have been going through the trucks over the last year and a half replacing hoses, EGR's, compressors, turbo's, and other items that needed freshening up. My question is when should we be looking at the internals? I've heard of them needing a "bottom end" at around 750K . Is this necessary? Can a oil sample determine if this needs to be done? Mine now has 650K on it and I run AMSOIL in the truck. It has been running smoothly, and I don't want to spend a bunch of money on a repair that is not needed, even though Mack recommends it. Any thoughts?

I have a 2005 CX Vision which was formerly a Air Products truck and it is used to pull a 2003 Timpte Hopper. I had the local Mack dealer rewire it with a replaceable pigtail instead of the hard wired one. Now my trailer ABS light on the trailer is constantly on, and the ABS trailer light on the dash is on. Timpte has checked my trailer and it is OK. They tell me the ABS is working, but the ABS lights are not working because of the truck. Mack says it is wired to spec. I know if DOT sees it I will be cited. Even though Timpte says some trucks are not compatible, I think I have a wiring problem as it was working before. How can I determine which wires are not lined up properly on the buss bar or if there a wire missing?