Comment: I had a 1964 mf135 and no engine braking in high multipower. Long story short there is a component called "nosecone" in the gearbox. This mimiced perfectly a worn out multipower clutch pack. It fooled the experts, and this mechanic turned dealer had been around for 25 plus years. The nosecone was remanufactured and the gearbox worked like new. Problem: you need to pull the multipower clutch pack out to check any way to be sure. Not cheap.