What parameters actually trigger the computer to lock up the converter? Is it based on throttle position, speed, RPM, what gear you're in, or a combination of all these things?

I know it's good to be locked up at high speeds to save on gas mileage, but what's the benefit of the TC not locking up?

 

An unlocked converter allows torque multiplication. A locked converter is like a stick car at that point. No slippage.
Think of a converter as kind of a go kart clutch.

Lock up decided by a few different factors. They lock up in 3rd and 4th gear only. They unlock if you touch the brake pedal or give it 60% thottle or so. I think that some cars will not lock up until the engine reaches a specific temp????

 

Throttle position/speed/rpm/maf/engine temp all play a role in when the converter locks.

 

I'd like to keep my converter unlocked in 4th at low speeds. Right now, I "think" its locking up in 4th at very low throttle. With 3.73s, here's how car shifts at very low throttle...say in city streets driving slowly.

1-2 around 15 mph
2-3 around 25 mph
3-4 around 35 mph

Well, when my car hits 35mph, it shifts to 4th and then gets real sluggish. I "think" it's locking up. I can push the gas a good bit, and it'll "slip" and get moving, but there is a slight delay. Just enough if I was racing someone starting at 40mph...this would not be a good pause.

I've tried the touching brake thing and it does seem to unlock, but that's kind of a pain in the *** to tap the brake and then punch the gas.

If I reprogrammed the shift point so that the 3-4 shift would occur 5 o 7 mph higher, would that help?

 

The pro builders should chime in but - sounds like you want what an edit program ot shift kit/higher stall convertor will do. EDIT the torque lock up points, shift kit programms the up/down shifts, higher stall will allow that release while at lower mph and rpm