I'm looking for a way of slightly increasing line
pressure, to provide a crisper shift and to lengthen
band life, without using a handheld tuner.
If your tranny is computer controlled, and an 04 is, the only way is to have a reprogrammer. Sometimes a tranny shop can do custom shift points on electronic trannies but they won't guarantee their work, so if you don't like the way it acts you will have to pay them to put it back.
Have you checked TransGo for a valve body kit, might not be what you want but it is a start.
I've seen a couple one from superior another from transgo, I know lentech transmissions did a write up on a drag racing car with the same trans, they altered the line pressure by altering some solenoids. Either way if I get a tuner or take it to a shop it sounds like 400 bucks, I was looking to do this myself and Saving the money. Probably just do a fluid and filter change with synthetic fluid, maybe the superior kit while I'm down there.
I would recommend racing trans fluid also, and at least install a tranny temp gauge system.
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