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Old 02-12-2005, 10:33 AM   #1
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Default TH440-T4 Modifications

Instead of hijacking haro'* thread, I thought I would start a new one. There was the idea of removing the springs for the clutches to increase shift firmness. I was looking in my FSM.. and it seems that there is a Pressure Regulator that of course regulates line pressure.. still don't know where that is exactly, and how I could replace and/or modify that to increase the line pressure. But, it really seems like there isn't a whole lot I can do other than that. It seems like a good quality teardown would be the best option to increase the performance of the Transmission. Post up any ideas you have. And remember, my transmission is all hydraulic, so there are no electronic mods I can do.


-justin
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Old 02-12-2005, 07:04 PM   #2
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just be careful what you muck with. there'* a way to increase line pressure, but there'* also a pressure valve (which may be referred to as the pressure regulator, depending on who'* talking) that is there as a safety device - if the pressure exceeds what is safe for the tranny, it blows off the extra pressure. you want to make sure that when you go diving in, you mess with the right stuff... otherwise, you could be building yourself a time bomb...
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Old 02-12-2005, 07:09 PM   #3
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Hmm.. that'* what I was reading.. I thought that was to limit pressure. So, is the regulator [the one I want] just the limit of the pump? Or is there still a blow off valve for it?


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Old 02-14-2005, 09:01 AM   #4
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Quote:
Originally Posted by opensourceguy
Hmm.. that'* what I was reading.. I thought that was to limit pressure. So, is the regulator [the one I want] just the limit of the pump? Or is there still a blow off valve for it?


-justin
well now, i don't know which one you're talking about
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Old 02-14-2005, 10:42 AM   #5
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i just did some checking, and you're kind of out of luck, if what i'm reading, i'm reading properly. your pressure isn't controlled by a solenoid, like it is in the tranny i work with on a daily basis - it'* controlled by the vacuum modulator. The piston that'* driven by the vacuum is directly linked to the modulator valve, which controls the amount of line pressure. i don't really see any good way to give yourself a boost in line pressure there. the pressure regulators inside the pump that blow off the excess are a simple ball and spring setup. when the fluid pressure is greater than what'* accepted (There'* two in there, one for the tcc apply, at 100 psi, and another who'* value i don't remember), the ball pushes against the spring and blows off the extra pressure. i haven't checked out the t65, but i would imagine that theirs is electronically controlled...

<edit>

yeah, this is from the 65...

Quote:
The force of the accumulator spring and accumulator fluid
pressure together control the rate at which a clutch applies. In
the Hydra-matic 4T65-E, accumulator pressure varies in
proportion to the torque signal pressure acting on the accumulator
valves. Therefore, when torque signal pressure is high,
accumulator pressure will be high. Likewise, when torque signal
pressure is low, accumulator pressure will be low. Since torque
signal pressure is regulated by the pressure control solenoid,
(which is controlled by throttle position through the PCM), the
accumulator valves regulate accumulator fluid pressure in
proportion to throttle position to control shift feel.
Quote:
The Pressure Control Solenoid Valve (PC Sol. Valve) is a
precision electronic pressure regulator that controls transmission
line pressure based on current flow through its coil windings.
As current flow is increased, the magnetic field produced by the
coil moves the solenoid’* plunger further away from the exhaust
port. Opening the exhaust port decreases the output fluid pressure
regulated by the PC Sol. Valve, which ultimately decreases line
pressure. The PCM controls the PC Sol. Valve based on various
inputs including throttle position, fluid temperature, MAP sensor
and gear state.
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Old 02-14-2005, 03:53 PM   #6
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So, the Vacuum Modulator essentially controls when pressure is blown off, correct? I can get a 60-E Modulator which is adjustable.. but that'* it I guess, huh?

I'm still curious about the removing of the springs.. because I bet there is a decent amount of relationship between the Turbo 400 and the 440, so I may be able to get some springs from one of those.. or a spring replacement kit for one of 'em.


-justin
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