Chris, let me clarify what you stated about pressure: Pressure is not restriction to flow. It's the Product of restriction to flow. I'm pretty sure that is what you meant, but just wanted to clarify the point. I'm also sure that the guy that did the hydraulic design in these transmissions is in the nut-house... . or should be.
Let me qualify my thoughts: I am not an expert. I have the service manual in front of me, and as you stated, the hydraulic schematics are flawed, probably to confuse the dur***x designers, and other pedestrians. I could be quite mistaken in my conjecture, but humor me.
*** If the schematics are more incorrect than I perceive, then all bets are OFF! ***
If you have a service manual, follow along as I dig myself deeper into the quagmire..... If you don't have a manual, please be patient.
As I see it, on the fourth gear-lockup-not-applied schematic, converter lube pressure appears to be sourced from the regulator valve just above the torque converter illustration. lube pressure fluid flows into the middle chamber of the L/U switch valve, out the bottom and left to the torque converter front side, and elsewhere.
(If the fluid flows into the converter in front of the lockup clutch, it would tend to hold the clutch disk off the front cover. It wouldn't be pressure so much as just the flow holding it off. Assuming that's the way it works... . interesting!)
The fluid in the torque converter appears to flow out the right-side (or rear) of the converter to the bottom of the left-hand chamber of the L/U switch valve, then on to the cooler and to lubrication, whatever that is.
Now refer to the fourth gear-lockup applied diagram. When the lockup solenoid is activated, line pressure is applied to the left end of the lockup valve, and moves it to the right. The middle chamber of the lockup valve allows line pressure to be applied the the left end of the L/U switch valve, which moves right and shuts off the lube pressure from the torque converter routing it directly to the cooler and to lubrication circuits. It also applies line pressure to the torque converter back side through the same circuit that transferred the lube pressure out of the converter when it was unlocked. I guess this is how the flow reversal occurs. Now the diagram gets murky. When the L/U switch valve is in the right-hand position, lube pressure appears to be diverted through a hydraulic restrictor (just above the L/U switch valve in the schematic) and into a third chamber in the L/U switch valve which ports the restricted lube pressure to the torque converter front side, and the front clutch lubrication. The restrictor is going to limit the lube pressure because of its resistance to flow. The converter now has a pressure differential inside. Line pressure 95-130psi) is being applied behind the lockup clutch, and there is reduced lube pressure (somewhat lower than 5-60psi because of the restrictor) in front of the lockup clutch. The piston is going to try to get to the space of lower pressure, and will be forced toward the converter front housing by the line pressure.
It seems logical.
Oh yeah. The holes in the forward clutch housing photo are there to allow the entrained oil (probably that pesky lubrication oil) in the clutch pack to escape, giving a quicker apply.
SBC, (Peter?) Yes, I believe I've heard marcel mentioned in regard to auto transmission clutch packs. Good point. Thanks for the reminder!
I'm gonna be playing airplanes for the weekend, starting at 6AM tomorrow so I'll let you guys duke it out from here. There's a great deal to be learned here, and it's going to be fun to read the posts when I get back. Have a good weekend!
Tom
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