I went to my truck yesterday and the battery was dead. Jumped started it and drove to work and back home. Well I went out this morning and she once again was on the verge of being dead, barely started. My question is, which battery do I replace or are the batteries wired in parallel? Which I'm assuming would require both batteries to be replaced.

Batteries are wired in parallel, and should be replaced in pairs.
Double check the connections before buying new batteries (remove the cables from the battery), the sidepost terminals can get pretty rotten before it's visible on the outside.

Gracias, I was hoping that wasn't the case but assumed that!!

it's the one on the drivers side that is bad.

they are both the same age and would personally change both, just did this a couple months ago now I won't worry for years to come!!

Mine on the passenger side went bad. Just change them both.

Mine on the passenger side went bad. Just change them both.

X2. The problem with replacing just the bad one is that the other non-new battery will leach power off of the brand new one, thus shortening the new battery's life. The good thing is that pulling the OK battery out and replacing it with a brand new one will a) make the batteries in your truck last the longest they can, and b) give you a great battery for the garden tractor (if you can get it to fit).

they are both the same age and would personally change both, just did this a couple months ago now I won't worry for years to come!!
:exactly:Replaced with 2 red top Optima's just a couple of months back.

I had the same experience. I parked the truck on Tuesday night, and it would not start on Wednesday morning. I pulled both batteries and tested them with a Volt meter; they tested 11.7 volts (driver's side) and 10.8 volts (passenger side).

I searched the posts here and found that most folks were replacing the stocK AC/Delco batteries with Optimas or Interstates, and a few went for the Duramax from AutoZone.

I made my decision at the Intersate dealer, they have both Optima and Interstate, and went for the Interstate 85s with 2 year free replacement. The Optimas were out of my price range.