Quote:
Originally Posted by Formula413
I wonder what the danger might be of adding a lockup switch to my car? I would probably only use it in third gear, and sometimes fourth to keep it from unlocking itself. But why isn't it enabled for third gear from the factory? Am I risking damage by forcing lockup in third?
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This information is speculative, and is not to be taken on authority without further research.
My best thought on lockup not occuring from the factory in all gears is that under "normal" (foot through the floor) acceleration, the transmission wouldn't have time to lockup, unlock, shift gears, lock, unlocks, shift, lock, unlock, shift, lather, rinse, repeat. It would create unnecessary wear.
Also - lockup was designed for fuel economy in highway situations (40mph+ constant speed) and to stop the neutral lift problem that plagues auto tranny vehicles.. (when you lift off the gas, it essentially freewheels, engine speed drops to idle, and then you have to re-accelerate the engine to match vehicle speed, which is a waste of work and fuel, that happens a hundred or more times over the course of a basic 20 mile trip.)
If you research a bit further into newer automatic transmissions, some mfg's are actually starting to add full lock to electronic transmissions so that every gear allows the TC to lock 1:1 w/ the engine after the "initial take off" period (any time that lock would have the engine under a desirable RPM range.)
Those things said, I seriously doubt that if you spend any time in 3rd gear, using manual lockup would hurt anything... If you're only "passing through" 3rd gear, I wouldn't bother, really, unless you have exceptionally long gears and a high-stall convertor (like 2250 or higher.)