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Discussion Starter · #1 ·
Have a 2016 F-550 with a transmission problem.

- for a few weeks, the truck would hesitate to shift into first and move when cold: shift into drive, hit gas, *truck acts like it's in neutral*, wait 10 seconds and give a little more gas, *truck shifts into first and moves*

- then, while driving at highway speed, the truck acted like it shifted into neutral and from that point forward won't move

- with the driveshaft disconnected from the rear wheels, the shaft out of the transmission spins, but can be stopped just be grabbing onto it - it's not getting any power

The solenoid valve body has been replaced, and we aren't getting any codes.

Can a bad torque converter or pump cause this?
Does the pump need to be primed in some way to cause oil to start moving through it?

Any ideas?
 

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Sounds like a bad pump or possibly a clogged pump? Have you dropped the trans pan and changed or checked the fluid? What color is it? Was there lots of metal shavings/any flakes stuck to the magnet in the pan? How many miles on the truck/since last trans service?
 

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Discussion Starter · #3 ·
That’s what I’m thinking. The pump looks fine, but honestly I don’t know how to tell it’s bad. Regardless we have a new one ready to go in.

Oil was dark, but no metal.

Can a bad pressure solenoid cause this, or would the truck still move and torque converter just not lock up?
 

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The truck should still move with a bad pack, probably not well, but it should still move.
 

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Discussion Starter · #5 ·
The truck should still move with a bad pack, probably not well, but it should still move.
Thanks, that’s what I was thinking.

One more note: the PTO isn’t engaging, this also makes me think it’s the pump, as the pump is directly connected to the flywheel via the torque converter, right? Without pump pressure the PTO shouldn’t engage.

Still leaning towards pump, I just want to make sure my bases are covered before closing things up
 

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I remember watching a video a while back on a 550 that the PTO wasn't working, ended up being damaged wires on the passenger side door sill. Wires reconnected and PTO all good. They could be related in your case, but if you want to rule it out, a quick pull of the sill and see if your wires are damaged or not and you should know.
 

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Discussion Starter · #7 ·
I remember watching a video a while back on a 550 that the PTO wasn't working, ended up being damaged wires on the passenger side door sill. Wires reconnected and PTO all good. They could be related in your case, but if you want to rule it out, a quick pull of the sill and see if your wires are damaged or not and you should know.
PTO wiring is ok. The truck responds like the PTO is getting power, the gear just doesn't engage, which has a direct line from the transmission pump.
 
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