Shop Talk Blog

You’ve noticed that your CTL seems weak or sluggish, or maybe it loses power under load. Your first instinct is probably to assume your final drive motor is shot … but is it? That assumption proves wrong more often than you might think. In fact, a quick phone call with a tech can save you a $3,500+ mistake.

This blog post goes in depth on charge pump issues, what the symptoms are, and how to tell the difference from a failing final drive.

Why the Confusion Happens

We’ve talked about this before: both a failing charge pump and a failing final drive motor can cause similar symptoms. A loss of power and sluggishness are both symptoms that final drives and charge pumps can share. Understandably, people usually default to the final drive motor because it's the more commonly known/talked-about component. However, the underlying cause and fix are very different. And that’s why it’s so important to get a proper diagnosis before you start ordering parts.

When a final drive starts acting up, the instinct is to jump straight to "I need a new one." Sometimes that's true. Often it isn't. A weak charge pump, a clogged case drain filter, tracks set too tight, or a machine stuck in high-speed mode can all mimic final drive failure perfectly. And if you replace the drive without finding the real cause, you'll be back in the same spot in a few hundred hours, except now you're out the cost of a motor too.

This guide pulls together everything we've learned diagnosing final drives at Texas Final Drive. From the questions to ask before you even open a toolbox, to symptom-by-symptom troubleshooting, to the tests our techs actually run in the shop, you can find information here. Whether you're running a single skid steer or managing a fleet, the goal is the same: figure out what's really wrong before you spend a dollar fixing it.

Your Bobcat is down, one final drive is toast, and now you've got three quotes in front of you: OEM from the dealer, a new motor from a parts supplier, and a remanufactured one for a lot less. They can't all be the same, so what are you actually paying for?

Every one of those three options can get your machine back to work. But they're not interchangeable when it comes to lead time, cost, and what's actually backing you up if something goes wrong. Here's what's really different, and how to pick the right one without overpaying or getting burned.

Here are a few other Shop Talk Blog posts you might find of interest:

• Finding the Right Final Drive for Your Skid Steer or Compact Track Loader
• Bobcat Final Drives: Leaking Seals and Crossrobbing
• Bobcat Final Drive Basics

What "OEM" Actually Means (and What It Costs You)

OEM means the part came from Bobcat's own supply chain, carrying the Bobcat part number and built to the exact factory spec for your machine. There's no guessing on fitment, and for a machine still under factory warranty, it's often the only option that keeps that warranty intact.

Here's the catch: final drive motors aren't a part your dealer keeps ten of on a shelf. They're a special-order item on most models, and you can be looking at days to weeks of downtime waiting on a backorder. You're also paying full dealer markup, which is typically the highest of the three options by a wide margin.

OEM makes the most sense when:

• The machine is still under Bobcat's factory warranty and you need to preserve it
• You're required to use OEM parts for a fleet compliance or resale reason
• Lead time isn't your biggest constraint

Somebody's mad, and they have a right to be: just six months, maybe 400 hours, and their new final drive motor is acting up again. Did they buy junk?

Here at Texas Final Drive, we regularly open up final drive motors and the story of the failure is almost always written inside the motor. It’s not usually a manufacturing defect or a bad reman job. It’s often debris from the first failure that’s still living in the machine and ready to chew through a perfectly good replacement.

There’s a good chance that the drive isn’t the root cause. The system may have failed and got a fresh drive to devour.

What a Failed Final Drive Motor Leaves Behind

When a final drive motor fails, it never fails politely. We regularly see bearing races spall, pistons scuff, and the rotary group grind itself down. And all that metal goes somewhere. Fine particles may ride the case drain line straight back into the tank. Bigger particles hang out in the hoses, the cooler, the valve block, and the low spots in the hydraulic reservoir.

Here are a few other Shop Talk Blog posts you might find interesting:

• Case Drain Flow Testing: The One Test Most Operators Skip
  

• Why Rental Companies Trust Texas Final Drive 
  

• Don't Get Spooked by Your Final Drive!
  
  
  

If you've ever popped the hood on a 100°F+ afternoon and felt heat radiating off your machine before you even touched it, you already know what we're about to explain. That same kind of heat can affect your final drive motors, too. According to Brendan Casey in Machinery Lubrication, overheating ranks second on the list of the most common problems with hydraulic equipment.

We’re going to talk about what's happening inside your final drive motor when it's this hot, and what you can do about it.

Here are a few other Shop Talk Blog posts you might find interesting:

• Bobcat Final Drives: Leaking Seals and Crossrobbing

• 5 Gear Oil Mistakes That Can Kill Your Final Drive Motor

• Reman Final Drives in a Greener World

What Does Heat Do to a Final Drive Motor?

Here's the simple version of what's happening “under the hood”:hydraulic fluid is supposed to be thick enough to keep a protective film between all those moving metal parts inside your final drive (e.g., gears, bearings, the works). Think of it like the difference between spreading cold honey and warm honey. Cold honey holds its shape and coats things nicely. Warm honey runs thin and slides right off. Yourhydraulic fluid and gear oil do the same thing when the Texas heat gets into them: they thin out, and that protective film gets thinner right along with them.

On newer Bobcat models that share a common brake circuit, we've been seeing a failure pattern that starts small but takes out both final drives. And it might be affecting you! Read on to learn what it does and how to diagnose it on your equipment.

Most owners and operators don’t realize how important case drain flow is when evaluating and diagnosing a final drive motor. This test can tell you a great deal about what’s going on inside your final drive without having to open it up.

In this blog post, we take a look at case drain flow testing, including how to perform the test and how to interpret the results.

Internal Leakage

Internal leakage is designed to support lubrication and cooling of dynamic components (e.g., bearings, pistons, etc.). Now, this leakage never leaves the system. It will always be returned to the hydraulic reservoir, often via a low-pressure drain line. Internal leakage does not contribute to the work being done by the final drive motor, though.

There is a baseline case for the hydraulic motor drain flow on your machine. However, as wear increases internal clearances and internal seals wear out, the case drain flow increases. This directly reduces the final drive's volumetric efficiency.

Overheating is one of the earliest warning signs that something inside your final drive is going wrong. Before you hear grinding or experience a total failure, a steady rise in temperature often signals problems that you can catch early if you know what to look for.

In this Shop Talk Blog post, we’ll talk about what is considered too hot, then discuss the five key reasons why final drives overheat. We’ll wrap up with a quick review of what kind of damage overheating can cause and simple checks to address it.

Here are a few other Shop Talk Blog posts you might be interested in:

• Why Is My Skid Steer Acting Up?
• What Causes a Final Drive to Wear Out Prematurely
• Buying a Replacement Final Drive Motor
  

You probably maintain your tracks, filters, and attachments, but did you know that hydraulic fluid quietly destroys pumps and final drives when it’s neglected? Bad hydraulic fluid won’t fail overnight. Its effects are slow, causing excessive heat, accelerated wear, and power loss, until your equipment comes to a complete stop.

In this Shop Talk Blog post, we're looking at what it costs you to keep running your compact equipment on bad hydraulic fluid ... and the price is more than you budgeted for!

Here are a few other Shop Talk Blog posts you might find interesting:

• The Case Drain Filter: A Small Component That Prevents Big Trouble
• Why Rental Companies Trust Texas Final Drive
• 5 Warning Signs Your Final Drive Might Be Failing (And What to Do Next)

Just got your new or reman final drive motor and are having a little trouble identifying the ports? This Shop Talk Blog post is for you.

In this blog post, we’ll go over the four different categories of ports you can find on a final drive, what their purpose is, and how to identify them. For larger tonnage motors, we’ve also included a short video we made.

Here are some additional Texas Final Drive blog posts you might find helpful:

• Valve Blocks on Final Drive Hydraulic Motors
• The Ultimate Glossary of Terms About Hydraulic Motors
• What to Know Before You Order a Final Drive