--- title: A Gearbox Rebuild: What to Expect | Wolf Machine Reno url: https://wolfmachinenv.com/guides/gearbox-rebuild-what-to-expect/ business: Wolf Machine & Fabrication, Inc. address: 4812 Longley Ln, Reno, NV 89502 phone: (775) 359-5570 hours: Shop Monday-Friday 7:00 am-3:30 pm; closed Saturday and Sunday type: Metal and plastic fabrication and machining (custom and CNC machining, welding, metal and plastic fabrication, gearbox and part repair, align boring, metal spray) --- [Photo: Stock photo: a milling machine cutting metal under coolant spray] - [Home](https://wolfmachinenv.com/) - [Shop guides](https://wolfmachinenv.com/guides/) - A gearbox rebuild: what to expect # A gearbox rebuild: what to expect A gearbox rebuild is a teardown, a full inspection, repair of whatever has worn and a careful reassembly with new bearings and seals. Noise, heat, oil leaks and metal in the oil are the signs one is due. Stock photo: a milling machine cutting metal under coolant spray Key takeaways - The signs: noise, heat, leaks and metal in the oil - Every part is cleaned and inspected before decisions are made - Housing bores and shaft fits are often the real cause - Worn fits are rebuilt, then machined back to size - Bearings and seals go in new at reassembly We rebuild gearboxes of any brand or size. People are often surprised by how much of a rebuild is metalwork on the housing and shafts instead of the gears. Here is the sequence, in the order it happens. ## Signs a gearbox needs rebuilding The box tells you before it quits. Watch for these: - A new whine, growl or knock that changes with speed or load - Heat at the case, or oil that discolors quickly - Oil leaks at shaft seals or the case joint - Metallic flakes or glitter on the magnetic drain plug or in a sample - Shafts with end play or movement you can feel by hand ## Step 1: teardown and cleaning The box is drained and taken apart with attention to how each part sat, so assembly can follow the same order. Gears, shafts, bearings and the case are cleaned so wear marks and cracks are visible. A dirty part hides what is wrong with it. ## Step 2: inspection Each part gets a careful look. Gear teeth are checked for pitting, scoring and broken or worn faces. Bearings are checked for roughness and play. Shafts are checked for journal wear, damaged keyways, grooved seal areas and straightness. The case is checked for bore size and round at every bearing seat and for the alignment of the bores to each other. On steel gears, shafts and cases that have failed or run hot, [Magnaflux](https://wolfmachinenv.com/services/magnaflux-inspection/) can show cracks that are invisible by eye. Our guides on [repair or replace](https://wolfmachinenv.com/guides/repair-or-replace/) cover how those findings change the plan. ## Step 3: the findings call With the parts inspected, you decide what to repair and what to renew. Gears worn through are replaced. Bearings and seals are renewed as a rule. Shafts and housings that are salvageable are repaired. We have rebuilt gearboxes for the mining industry, saw mills, power companies and the printing industry. ## Step 4: housing and shaft repair This is the machine shop's part of the job. A bearing bore worn oversize is built up by [metal spray](https://wolfmachinenv.com/services/metal-spray/), a sleeve or weld and bored back, using [align boring](https://wolfmachinenv.com/services/align-boring/) where several bores have to share one line. A shaft journal or seal area is rebuilt and turned to size. Keyways are recut. Faces that seal against covers are trued so the joint seals. ## Step 5: reassembly and checks New bearings and seals go in. Gears are set to the right contact and backlash, shafts are checked for free rotation, and the case is closed and filled. Rotating parts that need balancing are balanced by an outside balancing shop that we arrange after machining. ## A word on downtime Plan the gearbox rebuild with the plant or machine schedule in mind. Ask for the findings call as early as you can, since decisions on gears and bearings drive the rest of the job. Having the old oil sample and the nameplate photos ready speeds that first conversation. ## What to send Photos of the nameplate and the case, the symptoms, and what the box drives. If you can open an inspection cover, photograph the gears. Call [(775) 359-5570](tel:(775)%20359-5570) or attach the photos to the quote request. See also the [gearbox repair](https://wolfmachinenv.com/services/gearbox-repair/) page. ### Sources - [AGMA, American Gear Manufacturers Association](https://www.agma.org/) (2026-10-18) - [Thermal spraying (Wikipedia)](https://en.wikipedia.org/wiki/Thermal_spraying) (2026-10-18) ### Talk to the shop [(775) 359-5570](tel:(775)%20359-5570) | Monday to Friday | 7:00 am - 3:30 pm | |---|---| | Saturday and Sunday | Closed | [Request a quote](#quote) ### Keep reading - [Gearbox repair and rebuilding](https://wolfmachinenv.com/services/gearbox-repair/) - [Metal spray](https://wolfmachinenv.com/services/metal-spray/) - [Align boring](https://wolfmachinenv.com/services/align-boring/) - [Repair or replace: deciding what to do with a worn part](https://wolfmachinenv.com/guides/repair-or-replace/) - [Sawmills](https://wolfmachinenv.com/industries/sawmills/) ## More guides Sending a job to the shop October 18, 2026 5 min read ### What to put on a drawing before you ask for a quote A drawing a machinist can quote from shows the material and condition, every size with a tolerance or a general tolerance block, the threads, any surface finish that matters, the quantity and the revi Machining October 18, 2026 5 min read ### Signs a machine needs align boring A machine probably needs align boring when pins bind, bushings wear out far faster than they should, bores have gone oval, or a pin that used to slide through now will not. These are signs that bores Repair and rebuild October 18, 2026 5 min read ### Repair or replace: deciding what to do with a worn part Repair when the part is sound, the wear is in one place and the original size can be put back. Replace when the damage runs through the part, when a crack cannot be removed, or when the failure will s Repair and rebuild October 18, 2026 6 min read ### Metal spray, sleeve or weld: rebuilding a worn surface Metal spray suits bearing and seal surfaces where you want little heat in the part, a sleeve suits a surface that needs a fresh hard face, and weld build-up suits parts that need strength across the r Repair and rebuild October 18, 2026 5 min read ### Getting a machine ready for line boring in the field Before a portable line boring visit, make the bores reachable, clean and supported, take out the pins and bushings, and have power and light at the machine. Then send the shop photos, bore sizes and t [All guides](https://wolfmachinenv.com/guides/) ## More from the blog Sending a job to the shop October 18, 2026 4 min read ### How to photograph and measure a broken part Photograph the part on a plain surface in bright light with a ruler or tape measure in every shot, cover every face, and add close-ups of the wear or break. Then measure the key diameters and lengths Machining October 18, 2026 4 min read ### From one prototype to a production run A prototype is made to learn whether a part works, and a production run is made once the design is settled. The steps in between are locking the drawing, building fixtures, checking a first part again Northern Nevada industry October 18, 2026 4 min read ### What TRIC's growth means for repair and machining work Storey County, home of the Tahoe-Reno Industrial Center, went from 870 private manufacturing jobs in 2015 to 15,168 in 2025, and the Reno-Sparks metro area went from 20,500 manufacturing jobs in Augus [All posts](https://wolfmachinenv.com/blog/) ## Questions people ask Still have a question? Call [(775) 359-5570](tel:(775)%20359-5570), Monday to Friday, 7:00 am to 3:30 pm. ### Will you rebuild a gearbox that has no manual or parts list? Yes. Inspection and measurement of the parts give the sizes needed, and we can machine parts from samples. ### Should I change the oil before I send the box? Do not clean the box inside. Send a sample of the oil with metal in it if you can, because it tells us what failed. [Photo: Stock photo: a lathe turning a bar, hot chips flying] ## Request a quote Tell us what you need, attach a drawing or photos of the part, and we will get back to you during shop hours. Free consultations; prompt estimates. [Call (775) 359-5570](tel:(775)%20359-5570) - From your specifications, drawings or samples. We can also assist you in designing your product or part. - Free consultations and prompt estimates - Stands behind the work: Our rates are very competitive and our quality is second-to-none. Wolf Machine stands behind the work we perform. - Company accounts: all major credit cards, or we can open an account for your company Shop hours Monday to Friday, 7:00 am to 3:30 pm. Send your request any time and we will get back to you during shop hours. Stock photo: a lathe turning a bar, hot chips flying