Still running after 70 years: inside the overhaul of a 1956 SYMETRO™ Gear Unit

The story matters beyond a single machine. It shows what becomes possible when sound original engineering meets disciplined maintenance and expert service: equipment that runs reliably long past its expected life. In an industry where every hour of unplanned downtime is lost production, that reliability is what protects output.

What the overhaul covered

We carried out the work during a scheduled shutdown, with one goal - restore the mechanical integrity of the drive. Our engineers:

• - Replaced all spherical roller bearings on the high-speed and intermediate shafts
• - Installed a new high-speed shaft (pinion) housing and realigned the shafts to specification
• - Verified tooth contact, backlash, axial displacement, and shaft positioning
• - Inspected the lubrication system, seals, and structural components

After 70 years under the heavy, variable loads of a working ball mill, the gearing told its own story: tooth contact remained correct, with only localized pitting on the low-speed gear set - well within tolerance for equipment of this age.

A fit problem, solved by engineering - not by force

Fitting the new housing surfaced a challenge: its mounting holes did not match the original 1950s pattern. Rather than force the fit and risk the alignment, our team machined the housing to the historic foundation geometry. That preserved both shaft alignment and the rigidity of the whole assembly.

Work like this depends on respecting the machine's original tolerances and choosing the right measurement methods. It is the core of a professional gearbox overhaul - and the reason a 70-year-old unit can return to service performing like it should.

Ready for the years ahead

Post-assembly measurements confirmed the gear unit meets every requirement for continued operation, with all clearances and axial settings within factory norms. We also used the shutdown to prepare the unit for vibration monitoring - the foundation of a Condition-Based Maintenance (CBM) strategy that catches wear before it becomes a failure.

Seventy years after it left the factory, the SYMETRO™ TS 1250 still transmits more than 1,250 HP. That is what initial engineering, material quality, and service competence add up to over time.

What this means for your installed base

A 1956 gear unit still running in 2026 is not lucky. It is designed to last, supported by the right service at the right moments. If you operate aging gear units - MAAG or otherwise - the same approach can extend their service life, reduce downtime risk, and prepare them for condition-based maintenance.

Talk to MAAG Gear about your installed base: https://www.maaggear.com/service-and-aftermarket#contact