How to Read a Gearbox Nameplate and Find a Replacement Unit
How to Read a Gearbox Nameplate and Find a Replacement Unit
When a gearbox fails, the fastest way to a replacement is not a phone call — it is a photograph of the nameplate. Almost every quote we issue at WGT starts with one. This article explains what each line on a nameplate means, which fields actually matter, and what to do when the plate has been painted over or lost.
What is on a typical nameplate
| Line | Meaning | Why you need it |
|---|---|---|
| Model / Type | Frame or series designation, e.g. K187, NMRV130, F87 | Sets the mounting footprint and centre distances |
| i (ratio) | Total reduction ratio, e.g. i = 24.83 | Sets output speed |
| n₂ | Output speed in rpm | Confirms the ratio against the motor |
| Nominal torque | Nm at the output shaft | Sizes the unit |
| Mounting position | M1–M6 designation | Determines oil level and breather position |
| Serial number | Unique unit ID | Lets the maker retrieve the original build record |
| Year of manufacture | — | Tells you whether better options now exist |
The three fields that decide interchangeability
For a replacement to drop in, three things must match:
- Mounting and shaft interface — foot pattern, flange dimensions, hollow or solid output shaft, shaft diameter and keyway.
- Ratio — and therefore output speed at your motor's rpm.
- Torque / frame size — the new unit must be rated at least as high as the original at your actual duty.
Everything else — paint, colour, brand badge — is cosmetic.
Mounting positions explained
Gearboxes are built with a defined mounting position, usually marked M1 to M6. It is more important than it looks:
- It sets where the oil level plug sits — overfill or underfill causes overheating or dry running.
- It sets where the breather and drain go.
- A unit designed for M1 cannot simply be rotated to M3 without changing plugs, and in some designs without changing the internal oil routing.
If you are replacing a unit in a position where there is no room for a like-for-like swap, say so at enquiry stage — orientation changes are handled in the factory, not on site.
When the nameplate is unreadable
In practice, about a third of replacement enquiries we receive come with a nameplate that is painted, corroded or missing. In that case, measure instead:
- Centre height of the output shaft from the mounting face
- Shaft diameter and keyway dimensions
- Bolt hole pattern of the foot or flange
- Distance between input and output shaft centres
- Output shaft speed measured with a tachometer, with the motor running
Those five measurements, plus a photo of the unit in position, are usually enough for us to identify the equivalent. Our search by model page also lets you look up common series directly.
Cross-brand replacement
If the failed unit is from a European brand, you do not have to buy the same brand. WGT manufactures direct replacements for SEW, FLENDER, NORD and Bonfiglioli series with matching mounting dimensions and ratios. This is common practice in cement, steel and material handling plants, where an identical footprint with a shorter lead time is worth more than a badge.
Two things to check before going cross-brand:
- Internal gearing may differ even when the housing matches. Ask for the torque rating at your duty, not just the model equivalent.
- Accessories — backstops, cooling fans, oil pumps, motor adaptors — must be transferred or re-specified.
A short replacement checklist
- [ ] Photo of the nameplate, straight on and in focus
- [ ] Photo of the gearbox in position, showing the driven shaft and any coupling
- [ ] Motor nameplate: kW, poles, voltage, frame
- [ ] Duty: hours per day, shocks, ambient temperature
- [ ] Any space restriction that prevents a like-for-like swap
- [ ] Whether spare parts (shaft, gear set, bearing kit) are acceptable instead of a whole unit
Send those to WGT via the contact page and you will get a specific replacement model with dimensions and lead time, usually within one working day.
Frequently asked questions
Can any gearbox be replaced by a cheaper equivalent?
Mechanically yes, if mounting, ratio and torque match. Commercially, the saving is usually largest on older European units where the original has long lead times.
What if the ratio on the nameplate is not a round number?
That is normal. Real ratios are often like 1:24.83 because they come from combined gear tooth counts. Give us the exact value — do not round it, or the output speed will drift.
Do I need to keep the same mounting position?
Only if you want a drop-in swap. If the machine is being reworked, the position can change, and so can the gearbox.
