batt.???

If you have time to let it sit overnight or a day or so, then unhook all of the cables from all the batteries and then after letting them sit a day or two if possible, check the voltage from each one, put a load test on them, and if you have a bad one, it should show itself! good luck! I've heard lots of truckers say that they can only get one year/maybe two years out of new batteries on their trucks.

 

U can take them to auto zone and they can load test for u.The duralast bat they sell is a good battery.I've had 4 of them on for 2yrs and they are still strong. I bet u have at least 2 bat that are bad.Good luck

 

4 years is old but clean connections first, most times that will fix starting problems

 

If you had to boost a couple of times, chances are they are toast. Even one bad battery will wreck the others. 4 years old is pretty good, they had a good life. You still need to check for any power draw with the key off. If you have a test light you can do this your self. Unhook all the main ground cables between the batteries and truck. Also unhook any ECM power/ground connectors if you can find them. Make sure everything is turned off and the doors closed. Install the test light between one of the main ground cables and a negative post on the batteries. A dim light is ok, this is from the radio and anything else that needs some memory power to keep clocks running or stuff like that. If your test light is bright something is using power even though it is turned off and that is killing your batteries.

 

Load testers are cheap!
Saw a flyer from harbor freight recently offering them for about $20

 

Just my opinion here Mike, but...
I always replace batterys in sets. If two are gone, i doubt the other two are far behind?
I dont want to worry about my batteries in the middle of the winter.

 

I would replace all 4 in a complete set too.