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Old 11-09-2011, 11:55 AM
TNC TNC is offline
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Join Date: Nov 2011
Location: Hawley, TX
Age: 63
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Vehicle: 2012 Dodge Ram Express
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I'm hardly an auto tranny expert, but I did get some decent exposure to locking converters and tranny issues because of owning some GM 700-R4 equipped vehicles over the years. On the original question, I'll say that most all modern auto trannies have lockup tc's. These have almost become a requirement due to fuel economy and even a wear factor for reliability. TC's with lockup basically have some kind of clutch mechanism that engages the output from the crank to the drivetrain in a pure mechanical state rather than a hydraulic pressure or fluid drive manner. You can see that a mechanical direct coupling when that coverter is in lockup mode is going to be more efficient than the hydraulic pressure mode. It will also generate less heat in the tranny when the tc is locked up.

Now as to what causes the lockup equipped converter to engage at a given point, I think different factors can be applied depending on design. I think the most common is computer control based on rpm, load, speed, etc. Other factors can come into play of which I'm not as well versed. As far as how you know your converter is locked up or not, some vehicles used to have an indicator in the earlier days and some may still have that. However, on most vehicles today with lockup tc's that I've seen, you almost have to watch the tach to detect or know when it engages and disengages. Lockup tc's have become so common that you don't usually get any indicator for tc lockup.

Again, I'll clearly state that I'm no tranny expert, and some of what I've said does not apply to all vehicles by any means and should be considered somewhat general as it applies to our Dodge trannies.
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