Guide
Gearbox strip-down and diagnosis: why the first price is an estimate
Updated
Every honest gearbox quote has two stages. The estimate before the strip, and the price after it. Anyone giving you one firm number over the phone is guessing, and the guess is priced to protect them.
Why symptoms are not enough
A whine can be a bearing worth a modest bill or a set of gears worth many times that. A gearbox jumping out of gear can be a worn selector detent or a shaft running in a housing that has gone oval. Until the unit is apart and measured, the specialist is working from probability. Firms that quote a firm price from symptoms alone either load the number to cover the worst case, or issue a low number and revise it upward once it is stripped. Neither helps you plan.
What the strip fee should buy
- Dismantle, clean and measure every component that matters: bearings, gears, shafts, housings, casing and mating faces.
- A written report naming what has failed, what is worn but serviceable, and what needs machining.
- Photographs of the failed components, so you can see what you are being asked to pay for.
- A firm price for the repair and, where they are available, for the recondition and exchange routes as well.
- An opinion on the cause, not just the failure. Misalignment, contaminated or wrong-grade oil, overload or a failing coupling will do the same damage again.
The questions to ask before you send it in
- What is the strip fee, and is it credited against the repair if I go ahead?
- What do I get if I do not proceed? The report, the photographs, and the unit back, and is it returned assembled or in boxes?
- Who pays carriage each way, and is collection available?
- How long from arrival to report? This is the part of the lead time that is within their control.
- Will you quote all available routes, or only a rebuild?
Find the cause, not just the failure
The most expensive gearbox job is the one you pay for twice. Before the unit goes back in, deal with what killed it: check alignment and coupling condition, confirm the oil grade and change interval, look at whether the drive has been running overloaded, and check breathers and seals that let water and dirt in. On industrial plant this is also the maintenance duty in practice, since HSE guidance on PUWER requires work equipment to be maintained in an efficient state, in efficient order and in good repair, with the maintenance log kept up to date where machinery has one (HSE). On a vehicle it is usually the clutch, the mounts or a driveline problem that took the box out in the first place.
Keep the strip report. For an industrial drive it is maintenance evidence, and for a vehicle it is what supports the resale or the warranty claim later.