what do you think is wrong with my truck?

You need a battery with high cold cranking amps. If your stereo is high power and running amps and subs, you need a high amp output alternator

What you want to pay interest for is this. at the same time as the truck is placed into opposite does the engine replace revs. once you shift from park to opposite or stress the engine idle ought to drop. in case you do not listen the engine idle drop then the trans is both low on fluid or lengthy gone kaput as reported earlier. examine the fluid lever and note if its black in shade or pink, it would properly be pink. one situation that would ensue is the tranny would have water in it. This befell to me, my trans cooler in my radiator became leaking and putting fluid into the trans, which destroyed it. This brought with reference to the trans to fasten up and the idle under no circumstances replaced from park to emphasise. If it became basically the opposite equipment undesirable it ought to nevertheless roll down the driveway, sounds like something else of the tranny is about to flow also.

orange is absolutely correct, but i'd also check to see if that new tune box has a parasitic drain, as in it's taking power from the battery even when everything appears to be off