starter drags when cold (hard starting)

Have the batteries load tested...cheap way to rule them out as the problem.

 

How many miles on the truck? Each terminal (if loose or corroded) in the loop between the starter and batteries is a potential resistance that would limit your available CCA.

 

starter solenoid?

 

I highly doubt that 8 month old batteries will be having a problem. But I would suspect your cables. How old are they? Do you really have a good ground? Does the ground from the batteries go to the frame or the engine itself? Can you attach the ground to the starter and problem seem to go away? Even though one might think a engine makes for a good ground, some times it does not.

Now when was the starter last serviced? If your batteries are fine, and all connections are good, you then need to start looking for starter probs. The starter has a big job in trying to get things going. Again its a matter of connections. How clean is the terminal where the battery positive connects to the starter? Thats the simple of it all.

If you can, and your starter has been on the truck for say 2 years, try a different starter. Brushes wear, connections inside do go bad. Where the starter bolts to the block, is it connecting to clean metal? Or did you decide to customize your rig and get a good coat of paint across the surface where the starter mounts? Yep paint can weaken the starter, your not the first or the last soul to do such a thing.

 

connections can look "clean" take them apart, clean them to shiny reassemble and seal the connections with either grease or spray on battery post sealer . If you use grease coat each component as you assemble it. Watch the voltmeter as you crank the engine. do you have a draw in the system that pulls the batteries down when the truck sits?

 

How old is the truck ?? Cables do go bad !!!!

 

Just for giggles. Hook up jumper cables from battery negative posts to starter/motor ground points and see if that changes anything.
Have a friend that had starter problems and he replaced everything (batteries, starter, alternator) trying to find problem.
While BS'ing one day, about starting problem, we tried the above and starting problem was found......