Updated · By the AMS Parts team
Final drives rarely quit without warning. Most of the time the machine has been telling you something for a while—a little oil on the track, a noise in the turns, one side that's a step slower than the other.
Catch it early and you get to pick when the machine is down. Miss it and it tends to go on a Tuesday morning with a truck waiting to be loaded. These seven apply to excavators and compact track loaders.
1. It pulls to one side or travels weak
If one track is slower or weaker than the other, the drive on that side is a suspect. It's not the only possibility, though. Check track tension first (tracks run too tight are hard on drives), then the case drain filter, then whether a two-speed motor is stuck in high. If those check out, the drive is the next thing to look at.
2. Oil behind the sprocket
Oil on the inside of the sprocket usually means the floating face seal (duo-cone seal) is leaking. Gear oil leaks tend to be small and thick. A big, thin leak is more likely hydraulic oil from the motor.
If you see oil on the sprocket, it's probably time to pause and assess. If oil can get out, mud and water can get in, and that's what often takes out bearings and gears. If you are able to reseal and add oil, we strongly recommend keeping a close eye on the final drive, as it could lead to a major failure.
3. Grinding, growling, or clicking
A growl or grind usually means worn bearings or chewed-up gear teeth. Clicking or knocking that gets worse in the turns points to something loose or broken inside. A high-pitched whine is more often on the hydraulic side, which could mean low oil to the motor or a brake that isn't releasing.
If this is your symptom, we recommend tearing the gearbox down and doing an assessment of the parts. We recently had this issue on one of our yard machines and decided to replace it with a new option instead of investing in new parts and extensive labor.
4. Popping or banging
Park it. That sound usually means something big broke inside. Keep running it and you'll spread metal into the travel motor and possibly the rest of the hydraulic system. This can get extremely costly. What started as a final drive job turns into a much bigger bill.
5. Vibration or shudder
Check the sprocket bolts first. A loose sprocket will shake, and it's a quick fix. If the bolts are tight and it still shudders, look at the gears and bearings.
6. It's running hot
If you can't keep your hand on the hub, or water steams when it hits it, something is dragging. Low gear oil from a leak is the usual cause. A bad bearing, a dragging brake, or hydraulic oil leaking into the gear case can do it too. An inexpensive infrared thermometer makes the left-versus-right comparison easy.
7. What's on the drain plug
Pull the plug and look at the magnet and the oil. Fine gray paste is normal wear. Chips, slivers, or brass-colored flakes are not. A burnt smell or sludge means the gearbox is probably finished. Milky oil means water got in. If the oil level keeps creeping up, hydraulic oil is getting past the motor seal into the gear case.
One check doesn't tell you much. Watch how it changes over a few oil changes.
Making a drive last
Most dead final drives died of something small that got ignored. Check the gear oil on the schedule in your manual and change it on time. Change the case drain filter—a plugged one builds pressure and blows seals. Keep the tracks adjusted. Dig the packed mud out from around the hub so it doesn't grind on the seals.
If you do replace a drive, flush the system and change the filters. Leftover metal from the old drive will go straight into the new one.
Seeing any of this?
Send us a photo of the leak, the drain plug, or the drive tag, along with your machine's model and serial number. We'll tell you whether you're looking at a seal, a rebuild, or a new drive. Then read how to choose between rebuild, reman, and new, or find your final drive part number.
AMS Parts