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why billet torque converter


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@Dynamic will take us all to school on this, but from what I understand, a torque converter with a non-billet cover can tend to balloon with the extra oil pressure. A little bit of ballooning I think is normal, which is why we have a flex plate and not a solid flywheel. However when it becomes excessive, bad things happen. A billet cover helps combat this. There's probably more benefit than that however; that's just one thing I read a while back.

 

Edit:

 

Here's a video that shows ballooning. However I was wrong, it's the back plate, not the front cover.

 

 

 

 

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Okay I understand that after a certain amount of rotational speed/force things will distort. At what point does it become an issue for us especially with the low rotational speed of a Diesel engine? Is it the force applied on it or is it the speed at which it’s spinning or is it increased line pressures? Obviously engineers feel that a billet converter is not necessary in an engines stock form.. 

 

is a billet TC a sales gimmick up until a certain point and does anyone know what that point is? 

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I’d imagine it’s just because of the torque these engines can put out, not so much the speed at which it’s happening. That’s why Dynamic only uses triple disk converters in his builds. 

 

Gotta remember that engineers aren’t always engineering for the best application for vehicles, more like, what’ll get the job done and last long enough to where we won’t have to pay for it.

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The billet front cover is all about flex due to the converter clutch pushing against the inside of it. When the converter clutch applies, the apply piston simply pushes the disc(s) against the inside of the front cover, locking the turbine to the front cover. With increased pressures, the force with which the disc(s) are pressed against the cover increases also. Under heavy apply pressure, the stock stamped steel covers will flex, which makes the apply surface that the disc(s) is pressing against begin to take on a cone shape, reducing its apply surface. A billet cover helps to prevent (if not totally eliminate) this flexing and coning.

 

Converter ballooning can and does still occur, even with a billet cover. Ballooning typically takes place on the impeller side (back) of the converter, in the hub area, and is the result of excessive converter charge pressure. In a 47RE or 48RE transmission, the converter charge pressure is regulated (to about 130-135 psi) by the switch valve in the valve body. Much of the time, in forward gears, line pressure is not high enough to need any regulation (assuming a stock valve body here), but in reverse, where line pressures can be quite high even in stock form, this regulation is extremely important. Imagine backing a large trailer up an incline. You'll likely need a fairly significant amount of throttle to make things move. This will drive the line pressure to pretty significant levels, and without regulation from the switch valve, your converter will see ALL of that pressure, leading to ballooning around the hub. Now, enter the myriad of different "shift kits" and valve bodies that are on the market. Pretty much all of them will increase line pressure across the board at least a moderate amount, which is no problem, assuming an active regulator at the switch valve. BUT, I see many valve bodies come across my bench with either the switch valve land ground down (ie. our good friends at Transgo), or the balance hole in the separator plate blocked off. Both of these "mods" will remove the switch valve's ability to regulate converter charge pressure. Couple this with an increase in line pressure (sometimes a substantial increase), and you've go a recipe for a ballooned converter.

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