Steve,
I have the same situation. The spring is from the secondary pump check valve located in the shift housing. Drop the valve body, drop the shift housing with the plate. At the rear in a squared orifice will be the rest of the valve. Unscrew the housing from the plate to replace the valve. On this 126 the plastic valve housing broke and up to the pump she went, stripped the gear on the governor shaft, no upshift, no gov press. I do not have the part number with me at home but the cost was around 2 bucks.

This info is being provided by a clown that works in a dealership.

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Paul