Help with 47re (advanced diognostics)
 

So I have a 98 24v, 4x4 47re and it has no overdrive. Fluid is good, trans was rebuilt at some point.

Here's what I've done, I've started by checking ohm on od and lu solenoids and that was good (33ohms each)
Then I back probed the plug and went for a drive, at the point of overdrive command it dropped the 12 volts as it should, (but did not go into overdrive) and then shortly after, lock up dropped volts and convertor locked up as it should.
Then I went back to the shop and hooked up a pressure gauge to the overdrive port and went for a ride, 12 volt power dropped and the pressure gauge layed on zero. I was expecting to see the gauge jump up, meaning a big leak. But the gauge layed on 0, so I dropped the pan and pulled od and lu solenoids and bench ohmd them, still good, I put air into the port on the solenoid and air flows freely through the solenoid, when I apply 12v the valve closes as it should. So now that's where I'm at, where should I go next? I'm assuming it's something valve body related, maybe 3-4 shift valve or something, is that common to hang? I've done lots of reading but it's the usual "no overdrive" with a response of "put a mystery switch in, if it works its electrical, if it don't work, it's the solenoid", which we know isn't true lol there's a lot of other things involved besides a solenoid, although that is a common failure. Thanks in advance!

OD piston lip seal.


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I think you will find a valve body issue as ussually with a blown OD seal pressure will come up a small amount.

I was kind of thinking the same thing, because on the last lip seal I had blown out, I was getting like 70psi and there was a 2 inch piece of the seal gone. I guess being I have the pan off, would it be wise to drop the vb and apply shop air to the port on the case? Is there anything I can look for on the vb?

What is your main line (forward accumulator) pressure before and after OD is commanded?

I guess I did not check that. I dropped the vb, and applied air to the rear square port on drivers most side and I get loud hissing, and if I look up in the park rod hole I see no movement. I pumped some smoke up into the park rod hole and quickly put shop air to the port and the smoke rushed back pit through the park rod hole, so I'm assuming it's lip seal. But my question is where is the bleed hole at? If its in the back, it could be just the bleed off pushing my smoke back out. If the bleed hole is the round one next to the square ports then I deff have a big leak.