Electrical problems!!90 1/2 burb 5.7

[chevy4ever]

Ok, let me start by telling u what is going on riiight now.
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The Battery pos terminal is getting way too hot and burning up terminals. This morning it started but i noticed it was only reading 10vts... so when i got where i was going and tried to start it again it wouldnt start. The pos connection that was super tight 3 days ago when i last ran the truck was now loose. Its like its heating it expanding it or something. Well i tightened it and it started but still was reading low vlts. I turned it off again and this time when i tried to losen the pos terminal and retighten it it cracked.. It wasnt too tight but i think being heated caused it to weaken. Neway i replaced it with a nice brass one looks really heavy duty and tightened everything back up and it wouldnt crank the battery was dead. I jumped it and eventually it started. Well when i disconnected cables and tried to drive away it was still reading a lil under 10vts.and as i drove it dropped down to 8 and then completly died. I then had the alternator and battery tested and both passed. I redid the connections at terminals.. ground is good, the wire that runs to alt. is good and i replaced connection. The battery wire to starter is new and reran away from exaust. This is new motor as of like 8 months ago and i cant see that im missing something.
Now this elec prob started with the battery cable was next to exaust and burned and grounded out. I then replaced that. I wonder if that going on for awhile caused battery to go bad even though it test good.? Basically i see it as alt. is putting out allmost 13vts tested. Its either not really outputting that or it is and the battery is not getting it or the battery is not holding it. If the battery is not holding it i would figure that the engine would still run of the alt chargin. But the fact that it dies seems to me that the alt is not getting the power to the battery. If any of you have ne ideas please help!

90 burb 350 700r4 1/2ton 4x4