Transmission Issues

[Ashton'sExplorer]

2002 Explorer V8 Eddie Bauer Edition, 211k miles.
I recently replaced the solenoid pack, filter and fluid in the transmission. solenoid pack was replaced due to losing most gears and codes thrown. Drove it for one day, was much better (a few flares on shifting) and the O/D light came on. Parked it. 10 minutes later, transmission will not engage any gears, but Park. Shift cable is working correctly. Code given was PO775 (pressure control sol B ckt malfunction). Car sat for a week. Started yesterday, same thing, no engagement. Turned car off, started 10 minutes later, car shifted into gear like normal (did not take it out on the road, but all gears engaged in the driveway). Turned off, started up, no engagement. Any ideas? Electrical? Fluid related? I’m open to any suggestions. Thanks!

 

[BrooklynBay]

That code is usually related to worn servo bores. You could try the aftermarket servos with O ring seals.

 

[Ashton'sExplorer]

That code is usually related to worn servo bores. You could try the aftermarket servos with O ring seals.

That’s what I was thinking. Just couldn’t figure out why it would work intermittently.

 

[BrooklynBay]

The servos engage the drums with clutch plates. Leaking servos cause the drums to slip so you lose engagement. You could try to adjust the bands to see if the bands or the servos are broken.

 

[imp]

The servos engage the drums with clutch plates. Leaking servos cause the drums to slip so you lose engagement. You could try to adjust the bands to see if the bands or the servos are broken.

Um, don't the servos squeeze the bands around the clutch drums to keep them from rotating? The clutches are engaged by controlled hydraulic pressure, no? Unless automatics have been redesigned........

 

[Ashton'sExplorer]

The servos engage the drums with clutch plates. Leaking servos cause the drums to slip so you lose engagement. You could try to adjust the bands to see if the bands or the servos are broken.

Would that cause an intermittent issue? Just trying to figure out why it would come and go. Seems like if the servos were causing the loss of pressure, it would be constant. I’m stumped!

 

[BrooklynBay]

Um, don't the servos squeeze the bands around the clutch drums to keep them from rotating? The clutches are engaged by controlled hydraulic pressure, no? Unless automatics have been redesigned........

The clutch plates are hydraulically controlled as you mentioned but they are in drums which require servos to engage hydraulically to grab the drum with a band. The internal clutch plates won't do any good if the drum is slipping when it's supposed to be stationary. The band won't work correctly if the servo or the bores are damaged.

 

[BrooklynBay]

Would that cause an intermittent issue? Just trying to figure out why it would come and go. Seems like if the servos were causing the loss of pressure, it would be constant. I’m stumped!

Compare this to worn brakes. You step on the brake pedal but depending upon various conditions it sometimes stops faster than other times since the rotor slips while the brake pads are engaged. The caliper is compared to the servo. A damaged piston or caliper might leak, and cause a loss of hydraulic brake apply pressure. A sticking piston might not apply enough pressure or bind intermittently. Compare these things to your transmission bores, servos or bands.

 

[imp]

Compare this to worn brakes. You step on the brake pedal but depending upon various conditions it sometimes stops faster than other times since the rotor slips while the brake pads are engaged. The caliper is compared to the servo. A damaged piston or caliper might leak, and cause a loss of hydraulic brake apply pressure. A sticking piston might not apply enough pressure or bind intermittently. Compare these things to your transmission bores, servos or bands.

Well said!