Rexroth Final Drive

The final drives that we receive for evaluation, repair, or rebuild are not in like-new condition. In fact, most of them look like this Rexroth final drive from a Bobcat T140/T180/T190:

No technician with any love for machinery would dream of opening up a final drive for evaluation while it is in this condition (if it even can be disassembled!). In this article, we are going to go over our procedure for cleaning up a final drive prior to disassembly.

Why Cleaning is Important

As already mentioned, when we receive a final drive or track motor it usually arrives at our facility looking not unlike the image above: encrusted with dirt, mud, and clay that has been baked on. And that’s exactly what we expect, so don’t ever feel bad about sending in a final drive that looks like it’s made of mud and debris instead of steel and iron!

Before we would even dream of opening up a final drive, we thoroughly clean the exterior. This is necessary to prevent unwanted contaminants from getting into the drive when we begin to disassemble it, and also makes it easier to remove the bolts and separate the hubs when we get ready to evaluate and inspect the drive.

Rust and Caked-on Debris

The first stage of cleaning is to remove as much of the exterior debris and rust as possible. We use an air needle scaler to blast off scale, rust, cement, and any other hardened debris. This works very well as a preliminary step to washing and sand blasting. It is used to get the bulk of the material off the exterior of the drive. The image below shows the same Rexroth final drive as it goes through this process.

Wash Cabinet

The next step in the cleaning process is to place the final drive in a parts washer cabinet. Within the cabinet, the final drive is placed on a rotating turntable. Afer the parts washer door is secured and the timer is set, then this phase of the cleaning process is initiated. Detergent is sprayed on the final drive at high pressure from all directions. This removes grease, carbon, oil, and various types of grime in a far more effective way than could ever be done by hand. The image below shows the same Rexroth final drive being removed from the wash cabinet after the high pressure cleaning. You can already notice a significant change in its appearance.

Sandblasting

The next step in cleaning is abrasive cleaning, better known as sand blasting. We place the final drive in a large sand-blasting cabinet and proceed to blast away. The first image below shows the same Rexroth final drive as it is being rolled into the sand blasting cabinet.

This next image shows that very same Rexroth final drive as it comes out – looking like new, with all debris, scale, and rust completely removed. Now the final drive is ready to open up for inspection and diagnosis.

Conclusion

By taking the time to thoroughly clean the final drives as they come in, we are able to prevent contamination of the inside of the final drive when we do disassemble it. This cleaning process makes it much easier to loosen the bolts and separate the hubs.