no 1-2 shift - code P0781
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Joined: Jun 2011
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From: Indiana
no 1-2 shift - code P0781
my neighbor brought his 1998 F-150 to me to look at. Truck is 2wd, 4.6L and 4R70W trans with 247k on the odometer. He complained that most of the time the transmission would not shift from 1st to 2nd and the OD light off light was flashing. I retrieved code P0781
occasionally, the transmission would shift to 2nd gear but it would hold 1st gear until 6,000 rpm and then slam into second. once it shifted into 2nd gear the transmission worked normally.
I dropped the pan, valve body and found the 1-2 lower accumulator spring was broken.
While I had the valve body removed, I updated the pressure regulator valve with the Sonnax updated valve.
The stock pressure regulator valve shows significant wear
I also enlarged a few holes in the separator plate to make the transmission shift firmer.
Installed a new lower 1-2 spring and new accumulator piston, bolted on the valve body installed a new filter bolted on the pan then filled with fresh Mercon V fluid.
The end result is a transmission that shifts perfectly..
occasionally, the transmission would shift to 2nd gear but it would hold 1st gear until 6,000 rpm and then slam into second. once it shifted into 2nd gear the transmission worked normally.
I dropped the pan, valve body and found the 1-2 lower accumulator spring was broken.
While I had the valve body removed, I updated the pressure regulator valve with the Sonnax updated valve.
The stock pressure regulator valve shows significant wear
I also enlarged a few holes in the separator plate to make the transmission shift firmer.
Installed a new lower 1-2 spring and new accumulator piston, bolted on the valve body installed a new filter bolted on the pan then filled with fresh Mercon V fluid.
The end result is a transmission that shifts perfectly..
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