Fluid control in an auto trans pan

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panic
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Fluid control in an auto trans pan

Post by panic » Thu Jun 16, 2016 4:38 pm

Perhaps I'm overlooking something obvious, but should we be concerned about uncovering the pump pick-up on high-G acceleration?
When the front wheels come up, the fluid rushes backward and stands up on the back wall of the pan just like in the engine oil pan.
How does this not cause an air bubble to enter the pick-up, which will cause momentary loss of line pressure when that slug of fluid passes through the valve body, etc?

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Re: Fluid control in an auto trans pan

Post by Brian P » Thu Jun 16, 2016 6:00 pm

Have you tried putting a gauge on the line pressure to see if it's a real issue or not?

Loss of clutch holding pressure will cause slippage. Is it?

Suspicions (nothing more)
- The specified fluid level is high enough, and the orientation of the pick-up is such that the pick-up doesn't pull in air under that situation.
- In a drag-race start, the clutches needed for 1st gear are already engaged and the torque converter is already full of fluid, and the lock-up clutch (if there is one) is not going to be engaged at that moment. What it means is that there is actually not much demand for fluid volume at that moment. For the clutches to disengage, not only would the pump have to be sucking air but there would also have to be demand for sufficient fluid at that moment - for example, if the trans controls were commanding one of the other clutches to engage.
- By the time the trans controls are commanding some other clutch to engage (demanding fluid), the violent forces of the start aren't present any more.

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Re: Fluid control in an auto trans pan

Post by panic » Thu Jun 16, 2016 7:47 pm

Thanks, I suspected a few of your points but it helps to see them without prompting.

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Re: Fluid control in an auto trans pan

Post by ChevyEFI » Thu Jun 16, 2016 10:26 pm

Filter / pick-up location matter heavily. (top-feed filters are dumb, but the 200-4R has exactly that stock.)

Some of it will depend on power level and chassis. I have no idea what auto transmission stock filter picks up air at what power level, but I know I'm never sending out 700hp in front of a T56 without a pump. The gearset is fine, but no gearset is okay without lubrication.

Wild ass guess; Run a gauge and a way to cut power if the psi drops drastically.

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