The fixed modulators on early diesels are have a straight screwdriver adjustment under the 17mm cap nut (think its 17). As with movable modulators the key to the proper pressure is the eventual protruding length the device imparts on nthe valve inside the trans that it applies. A significant flair or soft shift can arise from putting a sealing washer under the device when screwing it into the trans. As the total length is the criteria adding the washer messes it all up. Move it in for harder shifts and out for softer. This trans is designed to have control presure control shift pressure and if no one has screwed the mod up then the proper mechanism for increasing shift strength is to make it shift later.

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