Massey Ferguson 398 Speed-Shift Fault

Charlie Admin • 30 September 2025

Massey Ferguson 398



Speed-Shift Fault


At JJ Farm Services, we believe in doing the job right, and that starts with a proper diagnosis. One of our recent workshop jobs was a Massey Ferguson 398 that had lost its Speed-Shift function. Here’s how we identified the problem and carried out a reliable repair.


Step 1: Starting with the Basics


Before we get into any major strip-down, we always begin with the simple checks. The first step was to inspect the hydraulic system, making sure the clutch pack was receiving the correct pressure. Without that pressure, the Speed-Shift can’t engage, but in this case, everything was spot on.


Step 2: Electrical Checks


Next, we turned our attention to the electrical side. A faulty solenoid or wiring issue could easily cause Speed-Shift failure. We tested the solenoid and confirmed that it was operating correctly. With both hydraulic and electrical systems working as they should, we were left with one conclusion…


Step 3: Internal Fault – Time to Split


The issue had to be internal. That meant splitting the tractor to access the Speed-Shift unit — not a small job, but necessary to get to the root of the problem. Once inside, the fault became clear: a failed Belleville spring. This small but crucial component had given out, causing the loss of function.


Step 4: Repair and Replace


With the Speed-Shift unit removed, we ordered the necessary replacement parts, including a new Belleville spring. While we had it apart, we also fitted a fresh set of friction plates. Preventative maintenance like this is a smart move, no point putting worn parts back in when everything's already open.


Why It Matters


Jobs like this highlight the importance of a thorough diagnostic approach. By checking each system methodically, we avoid unnecessary work and make sure we get straight to the root of the issue.


Need help with a similar fault?


With decades of hands-on experience, our technicians know exactly what to look for when diagnosing complex faults like this one. That expertise means less downtime and peace of mind for our customers. If your tractor's not shifting as it should, or you suspect something isn’t quite right, get in touch with our team. We’re always happy to help keep your machines working hard.



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