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So I've come across some literature that says it's a good idea to remove the reverse boost feature on all builds that contain an upgraded pr spring, regardless if it's a modulated or fixed line pressure setup, and also it's a must when converting to full manual control.
Now I know that with a Jakes D3, the reverse boost is already killed so no need to perform the modification to the pump or boost valve on that particular setup.
But what about an application rated for 1000 hp without a transbrake where higher line pressure is still needed? Let's say you want to get higher line pressure through use of a Sonnax LB1 boost valve and sleeve but with a stock PR spring to come in around 185 PSI. So in addition to blocking the reverse passage on the pump, with an LB1 boost valve, it looks like torque signal oil can still leak past the large land in the LB1 boost valve and still activate the reverse boost function, right? I know that with a stock PR boost valve, it gets modified by grinding a flat on the large land but wouldn't the flat still have to be ground on the large land on the LB1? I'm aware that another way to achieve all this is by not using the LB1, and simply modifying the stock PR valve and using spring rated for 185 PSI, but was curious on if the LB1 / stock spring setup and if it can also be modified to kill reverse boost? The double O-ring sleeve that comes with the LB1 is nice!
Yes I know: "why would you modify an already modified aftermarket part, just modify a new stock boost valve!" just wondering if anyone ever did this due to only having certain parts on hand and long shipment times atm.
Middle land on an LB1 is 0.8540 dia (top)
Middle land on stock is 0.830 dia (bottom)
Last edited by 5.7stroker; Nov 13, 2022 at 11:52 AM.
So I've come across some literature that says it's a good idea to remove the reverse boost feature on all builds that contain an upgraded pr spring, regardless if it's a modulated or fixed line pressure setup, and also it's a must when converting to full manual control.
Now I know that with a Jakes D3, the reverse boost is already killed so no need to perform the modification to the pump or boost valve on that particular setup.
But what about an application rated for 1000 hp without a transbrake where higher line pressure is still needed? Let's say you want to get higher line pressure through use of a Sonnax LB1 boost valve and sleeve but with a stock PR spring to come in around 185 PSI. So in addition to blocking the reverse passage on the pump, with an LB1 boost valve, it looks like torque signal oil can still leak past the large land in the LB1 boost valve and still activate the reverse boost function, right? I know that with a stock PR boost valve, it gets modified by grinding a flat on the large land but wouldn't the flat still have to be ground on the large land on the LB1? I'm aware that another way to achieve all this is by not using the LB1, and simply modifying the stock PR valve and using spring rated for 185 PSI, but was curious on if the LB1 / stock spring setup and if it can also be modified to kill reverse boost? The double O-ring sleeve that comes with the LB1 is nice!
Yes I know: "why would you modify an already modified aftermarket part, just modify a new stock boost valve!" just wondering if anyone ever did this due to only having certain parts on hand and long shipment times atm.
Middle land on an LB1 is 0.8540 dia (top)
Middle land on stock is 0.830 dia (bottom)
At some point in time, when you want to do modifications to a trans you have to learn to trace the circuits.
Can't be spoon fed forever.
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4L80E blocking reverse boost? 
