CAT 225 excavator track final drives issues and diagnosis

Cannot seem to find too much help elsewhere so going to see what I can find here.

We have an old 225 that we bought several years ago. We literally don't track it around and has really just been used to pick things up to put in trucks such as brush.

Back when we bought it, one of the track drive motors was loose, it was on the list for repair while thinking "who would do that?".... Anyway, I guess we forgot about it because the machine does not go anywhere.

Now we need it at full capacity and yesterday. Tried to track it and that track keeps stalling like it is getting in a bind. Tracks are not the best but verified the pitch does not exceed book spec and I tend to think the issue might be in the gearbox.

We thought it was the track brake because it was leaking bad into the final. I found the air breather on the top knocked off and water got in there, friction discs were toast, both springs were broke, input shaft was cracked from drive motor hanging on it (loose), and input bearing really toast.

I fixed all that really thinking that input bearing was my issue. Nope, still doing it.... I can creep along very slow and it seems ok but you know when you start going too fast and things start binding. There are no crazy noises, just the track stops and the engine loads up responding to the bind up.

The finals on these are linear, not planitary. Built pretty rugged. When I drained final oil, it was watered down for sure with pure water at the bottom, then the milky fun stuff. No steel chunks at all. However, looking in to see what I could, I did not see much corrosion in there and gears looked mint. Limited air exposure I guess....

I cannot be sure if what what might be hurt in the final or how to check. Looks like there are about 4 reduction gears with tapered roller bearings on each of the shafts. I am simply not sure if a bearing is damaged causing gear lash issues or what, or even how sensitive it might to a little play.

Confirmation of final issues is going to be a bad day. That will really suck to repair. These require the ENTIRE final removed from the carbody just to get the cover off, not to mention all the fun tools required for the job. I can get a few of the bearing covers off one side where I could possibly inspect things.

Just a thought, but I have seen binding when rollers are bad. I have seen rollers stop turning and then the chain wears deep grooves in them which puts a lot of drag on that track. That is easy to check out, just lift that side and look at the rollers.

Yeah, we were really hoping for a more simple find such as rollers or a chain that didn't want to move but even with track off the ground, the issue remains.

I am not sure if carrier rollers or even an idler issue would do something like this. It seems totally speed dependent though. If we just creep with it, it seems decent. However, we have not really tried to turn or move the machine just yet. I am pretty nervous to get a lowboy all the way out there to move the machine only to find out it can't even walk on the trailer.

Our plan right now to deliver the machine pretty much right to the place it needs used and try to minimize tracking until we can source the issue.

I figure the best way is just to remove the track and test the final but I might not like the result on that one......

My dad seemed to think the output sprocket shaft might be bent but I cannot really see that while watching it run.

What sucks is we just replaced a pile of dead lower rollers to make this machine ready to go and did not know we had further issues.

The previous owner really hurt the machine by doing squat to fix anything. Several flattened rollers to the point they could not be reshelled. That is hard on everything.

Rated drawbar pull is 36,000 lbs on the level, so 18,000 per side. If it does it with the track off the ground it must be in the final drive and be serious! Your best bet may be to find a good used final drive and change it out. That is not that big of a job and the machine is not down all the time it takes to find parts to fix the drive.

Any possibility of the drive motor causing this? Some have mentioned it but not sure I buy it. We have run the drive motor uncoupled and it seems to spin great. No leaks.

Well, if the motor runs fine uncoupled I would not thinks so, But you could swap motors from side to side and see if the problem follows the motor.

https://www.youtube.com/watch?v=xM8nV9c-Z5U

Here is a vid on the input shaft issues. I was able to pull that entire hub and rebuild it. That part is good as new.

https://www.youtube.com/watch?v=F8PHHbvu3ng

Here is a vid I did sometime back. The vid sucks but it might point to an issue. I am not sure what to make of the popping sound but it seems more like the chains to me.

I should also maybe point out how the track binds up. It is certainly not hard to drive the track so I know it is not in a constant bind. As it rotates, it would track along very normally and drive at the same speed as the other side. Then, without warning, the track seems to catch as in bind up, as if something got caught in the sprocket. It will then free up and spin normally.

Now, I have tried in vane to see if there is a certain point in rotation, a certain rpm, or anything that could point to particular component, but it seems almost at random. It goes like normal and in several point in 1 track rev, it will bind up and stall the track. I immediately get off the drive stick and try again, and it goes.

I know when I have seen gear lash issues in other systems, the bind would seem almost constant, like a brake dragging because the gears are sucking into each other.

I was also contemplating seizure of the roller bearings where they are flat spotted. Personally I have never seen them flat spot. they just seem to ride through it and get chewed up until the pins lose all tension such as the earlier input bearing vid.

I did notice the unusual wear on the sprocket that seems to be tapered on the tooth sides. Not sure if that is normal or not but you can see how it has pushed pretty hard in there but no shiny metal pops out to show major binding right now. maybe that is from turning with sloppy chains?

I looked at your vid's did not see much, you said you fixed the input bearings. Maybe do that motor swap and see what happens. The final drive is a triple reduction unit, so even when the machine is moving slow like in the vid that motor turns fairly fast, so it may have an issue at speed under load.

Ok, so if it runs normal most of the time and only binds for a moment, then my guess is that you have some broken teeth on one of the gears in the final drive and when they come around sometimes they bind some time it will go by if the load is not high at the time. The drive motor run too fast to cause this type of thing. Back to looking for a used final!

Thanks, I will do more testing on the motor.

Just for clarity, the two motor mount bolts were loose for who knows how long. I have not tracked the machine so it was not addressed until late. However, looking at the splines in the motor, it is obvious it spent some time tracking like this. So all 150+ lbs of that motor was mostly hanging on the motor shaft.


Do you think the case drain test might reveal much on the motor?

Stuff coming out of the track motor would be small and likely end up in the hydraulic filter. I think it is more likely a broken gear in the final drive.

Seeing that much play in the bearings
it's very likely you have broken gear
teeth. If a bearing allows a set of
gears under load like that to come apart
a bit it puts huge load on the tips of
the teeth and then things break.