4r70w Low Line Pressure and 0 psi EPC Tap
01-11-2015, 09:33 PM
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4r70w Low Line Pressure and 0 psi EPC Tap
Long time reader but first time poster.
I recently rebuilt my transmission and have greatly enjoyed the experience. Currently though I'm at my wits end here with why my line pressure is low across the board and my EPC line tap pressure is constantly 0 PSI at idle.
The transmission shifts 1-2 smooth, 2-3 somewhat rough (I can here a light thump,) 3-4 smooth but might be late (unsure.) Downshifts are fine.
I have bench tested the EPC solenoid and it applies. Additionally the resistance is within specs. In-vehicle testing has proven to be more difficult because I'm unsure if the program I am using (forscan) is actually controlling it (despite it being able to control the shift solenoids.)
My question is could someone give me further insight as to what/how the EPC solenoid works, how the PCM determines what it does and other possible causes of a 0 EPC pressure tap. Is this being caused by a leak further down in the value body? Maybe someone has the hydraulic diagrams of the 4r70w which I could study? A suggestion of better testing software? Questions are more than welcomed.
2002 Ford F150 V8 4.6L
P.S. Trying to fix the issue with the transmission still in the truck for obvious reasons but if it comes down to it I might have to drop it again.
I recently rebuilt my transmission and have greatly enjoyed the experience. Currently though I'm at my wits end here with why my line pressure is low across the board and my EPC line tap pressure is constantly 0 PSI at idle.
The transmission shifts 1-2 smooth, 2-3 somewhat rough (I can here a light thump,) 3-4 smooth but might be late (unsure.) Downshifts are fine.
I have bench tested the EPC solenoid and it applies. Additionally the resistance is within specs. In-vehicle testing has proven to be more difficult because I'm unsure if the program I am using (forscan) is actually controlling it (despite it being able to control the shift solenoids.)
My question is could someone give me further insight as to what/how the EPC solenoid works, how the PCM determines what it does and other possible causes of a 0 EPC pressure tap. Is this being caused by a leak further down in the value body? Maybe someone has the hydraulic diagrams of the 4r70w which I could study? A suggestion of better testing software? Questions are more than welcomed.
2002 Ford F150 V8 4.6L
P.S. Trying to fix the issue with the transmission still in the truck for obvious reasons but if it comes down to it I might have to drop it again.
01-30-2015, 01:25 PM
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It ended up being that I had the incorrect valve body separator plate gasket.
In 2001 they changed the separator plate gasket and added 5 new holes. I used a prior-to-2001 gasket which covered those 5 holes. It caused my epc pressure tap to be 0 and made the 2-to-3 shift very rough.
In 2001 they changed the separator plate gasket and added 5 new holes. I used a prior-to-2001 gasket which covered those 5 holes. It caused my epc pressure tap to be 0 and made the 2-to-3 shift very rough.
Last edited by connorm; 01-31-2015 at 10:43 AM.
