Got it! Interesting though, you'd think that a series of thinner clutches would do a better job. That's the idea behind motorcycle clutches (multi disk clutch packs) and our own auto trans. Considering that I'm looking at high quality OEM replacements, I think the multi disk thing might not be much of an issue. I'll make it a point to ask each vendor, just in case. Thanks for the 'heads up'!
Pretty close. Keep in mind, you're talking about two different things. The stator is all about torque multiplication and is strictly a mechanical device. Any time the two halves of the torque converter are spinning at different speeds, the stator is doing its redirection magic to increase the torque available to the trans input shaft. The TC clutch is all about torque application. When it engages, all slippage stops. Since there's no longer any difference in rotating speeds between the two TC halves, the stator no longer functions. (So you're right: both are spinning at the same speed.) The control module decides when to do this based on multiple sensor inputs (vehicle speed, boost pressure, engine rpm, clutch input shaft rpm, etc). Typically, with the engine at operating temp and above approx 40mph, the ECM/TCM/PCM will engage the TC clutch when it senses that engine rpm is matching trans input shaft rpm.
:thumbsup: Lowering my final drive ratio from 4.10 is a future project. I've got a brand new 3.73 ring and pinion set sitting on the shelf. All I need to do now is find a Power Trax Lock Right unit for a reasonable price and I'll be ready to get after it. See, over a period of time, my goal is: balanced, highly efficient motor + improved fuel supply/filtering system + high quality, low stall torque converter = 20mpg on a 7,000# truck. That's what's behind the search for a dual stator lock-up TC. Incredible torque multiplication, max engine torque available sooner (to match the torque curve, and a strong lock up feature to eliminate any slippage and inefficiency in transmitting movement and motion. Considering how strong the 4L80 is, this is gonna be ideal for anything I might ever want to tackle: towing, hauling, cruising, whatever. :agreed:
Here's the good and the bad. First the good: The TC is the wonderful piece of gear that give us automatic guys more 'at the trans' torque than the hand shaker folks ever dreamed of. We have the advantage of seeing our flywheel torque multiplied by over 150 percent. That means that the 385 pounds of torque that leaves the crankshaft translates into around 600 pounds of torque entering the trans. Very kewl. :agreed: But here's the bad: There's a price tag to this added torque - that multiplication only occurs when the two halves of the TC are rotating at different speeds. Specifically, the engine part (pump) is rotating faster than the trans input part (turbine). This slippage translates into heat and lost motion. In terms of overall mpg increases, the less slippage, the better. That's why the TC clutch was such a GREAT addition - it provided the torque multiplication we automatic guys love and the no-slip efficiency that the manual guys enjoy. Truly the best of both worlds. :thumbsup:
The purpose of the stator (and stall speed) is to provide torque to the trans when the engine is least able to supply it. So the TC is designed to stop working as the engine enters its torque curve. For us diesel folks, that means a much lower rpm than the gassers need. By setting up a TC to reflect your actual needs - load carried/towed, engine tune, typical road speed, etc - you minimize the time the turbine and pump spend at maximum slippage. Minimizing this time provides two benefits: it allows your engine to work effectively in its comfort zone, and it provides a slight increase in fuel efficiency.
Ya know, that sounds a lot like 'chuggle'. That occurs when the TC clutch is engaging and disengaging because road speed and load are right on the edge of the lockup parameters. Normal condition, just aggravating.
:thumbsup: :thumbsup: I'm converting to synthetic for the 'new' trans.
No real info on OEM stall. I've read and heard that it's in the 1300 - 1600 rpm range, but I can't find anything in my GM shop manuals that specifies. This morning, when I got to work, I pulled around back and did a quick stall test. Engine RPM climbed to 2100 and stayed there. So, that's the stall speed for my converter on my engine with my mods.