The way to tell whether its a three speed or four is the shape of the pan. The three speed is square with four bolts. The 4spd is rectangular with a narrowing to the rear (in the MB) with six bolts.

The kickdown arrangement on the 3spd is a plunger bolt/housing surrounded by the electromagnet. The pieces are bought separately. The plunger bolt unscrews from the case, tightens on the magnet and is sealed internally by two o-rings. The rings seal both ends of the bolts protrusion into the pressure passage. Leaks from either can simulate a engaged kickdown as its job is to leak away the pressure in the passage.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician