Good morning, I viewed your pics and the video and the top of the transmission looks very clean now!
I have searched Deere's bulletins and am attaching some info below for you to check.
Attachment #1 shows the primary(rear) variator.
The transmission was removed for the picture, but if you look under the back of your transmission from the bottom, you should be able to locate this area.
Let's make sure something isn't stuck in that linkage or that the variator isn't damaged.
I have also included a diagram that has the transmission components numbered.
Take a look and let me know if that helps at all.
The rear variator linkage is what returns the pedal to neutral. So something has to be holding it from returning to it's home position.
The only other thing I can think of without physically being in front of the machine, is the torsion spring at the pedal.
On the diagram, it is #7 on the last attachment. Take a look at that as well.
We may have had a combination of debris on the transmission and that spring may have broken. I don't have one these units here at the shop currently to compare to.
So I dont know how stiff that spring may be or if it has enough power to return the pedal to neutral.
I've never seen one break yet, but it is possible that yours is broken.
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