About a month ago I noticed my truck was experiencing hard starting. Sounded like it was laboring and taking longer to start. Didnt really think anything of if until I went to start it the other day and it almost didnt start but did. After I arrived at my destination (luckily it was my house) I went to leave and the battery was dead. No big deal I thought my battery must've been slowly dying. So I pulled the battery out of my wifes car and put it in and she started right up (still a hard start). So I drove the truck the rest of that day and after 4 starts that battery was drained till it wouldnt even try to turn the motor over.
I thought my starter was bad, so I pulled it took it to 3 different places and it passed all test. Put it back on, charged my battery, cleaned the shit outta all terminals around the battery and made sure everything there was tight. So now I was thinking maybe the pos battery lead running from batt to starter was my problem. Voltage on battery post 12.9, voltage on terminal 12.9, voltage on starter 12.7. Then I hooked my volt meter to the terminals and tried to start it. When I push the key forward (not enough to engage the starter) it begins to slowly drop the voltage (almost like a stop watch counting down) then when I try to start it it significantly drops voltage until about after 3 sessions of cranking for a couple of seconds of weak cranking it drops the battery to where it wont even try. So now I'm thinking I have 2 bad batterys, so I have them tested (at two different places) and of course they both check out fine. I have made no electrical changes recently and are not running any electronics other than an aftermarket cd player. Any help would be appreciated.
Oh yeah and once its started Im getting 13.9v at the battery and it doesnt miss a beat.