Upper Roller Bearings and Tracks Falling Off?

[Mark A Weiss]

Since I got my new tracks a couple years ago (they are somewhat longer, so the adjuster is 5" further extended), I've been having issues with tracks coming off the sprockets frequently.

I called my diesel mechanic (same guy who fixed my hydraulic line under the cabin in March) and he pointed out two things:

Tracks too tight
Upper roller bearings completely gone

I originally called him to adjust the big nuts that set the depth of adjustment for the track adjusters, but he's convinced it's these upper bearings. The roller sags about 2° as a result on both left and right tracks. He said that's guiding the tracks off the sprockets.

My original understanding was that the big springs that surround the pistons that comprise the track adjusters were what keep the tracks under tension, but he said that's incorrect that they are only there as shock absorbers.

So I've got a pair of these rollers on order now.






What do you guys think about the effects of this roller being off kilter? Is the mechanic correct about this?

 

[Nige]

he said that's incorrect that they are only there as shock absorbers.

He is correct. the hydraulic cylinder maintains the tension, the big spring is there for shock loads when you get something stuck in the track.

Since I got my new tracks a couple years ago (they are somewhat longer, so the adjuster is 5" further extended), I've been having issues with tracks coming off the sprockets frequently.

There's your problem right there. The tracks are too long and the hydraulic adjuster is over-extended.

 

[Mark A Weiss]

He is correct. the hydraulic cylinder maintains the tension, the big spring is there for shock loads when you get something stuck in the track.

There's your problem right there. The tracks are too long and the hydraulic adjuster is over-extended.

Well that was my thought, but the mechanic said that's not the problem. He in fact told me the tracks were over tightened. And he showed me where they are beginning to show cracks in the rubber from over stretch. (my original reason for calling him was to adjust the nuts that set the depth of the pistons.)

But what do you think about the upper rollers causing the track to be guided to one side and eventually off the sprocket?

 

[Tones]

Are the tracks coming off when reversing ( sprocket leading) or both directions?
Has the bolt that goes through the spring been checked? If that is broken it will cause (a) the tracks to look tight and (b) the tracks to flop off the sprockets.

 

[Mark A Weiss]

I don't recall if it was just on reverse. I do know that sometimes if I drive over a rock the affected track may come off. The last time the left track came off, I was driving straight backwards though. I suspect I've had tracks come off while driving forward as well.

 

[Tones]

Next time the track comes off pull the idler out, the spring should come with it. Then check the gap in the spring coils or see if the bolt moves. These bolts breaking isn't unusual, had one go on a new Cat 320 with 70hrs on the meter.

 

[Welder Dave]

The carrier roller looks pretty worn out but I don't know the original diameter. Being that the track has been wearing the mounting bracket, I would guess the rollers original diameter to be 2" or so bigger. It's not a lot but would still make the track tighter without using as much of the adjuster travel. If the bearings are shot could make the track go out of line.

 

[Vetech63]

Have the idlers been checked?

 

[92U 3406]

That carrier roller is done. Looks worn out and the bearings look like they're gone.

What's the idler look like?

 

[Mark A Weiss]

The idlers look fine. The mechanic also told me it looks like the previous owner had done a partial undercarriage rebuild, as the rollers on the bottom side all are in good condition.

I'm not sure what bolt is in the track adjuster that I need to look at. The track as to be completely removed to get at that, which is a LOT of work without a second machine to do the lifting.

 

[Tones]

It's the bolt that goes through the spring from 1 end to the other.
With a little bit of ingenuity your machine can pull out the ldler and stuff it back in.

 

[Mark A Weiss]

I know it can be done, and I did it when I had to replace a stuck adjuster and the track was completely off the machine. But that was an all day process and a lot of physical labor. Add in a recent heart attack and I'm not doing anything that physical for a while.

 

[Tones]

Fair enough.

 

[Mark A Weiss]

Here's the latest. The mechanic was hired to tighten the nuts to accomodate the longer tracks. He found that the upper roller bearings were shot. So we replaced those. Parts about $500.
Then he found that the check valve on the left track would not allow grease to go in. He tested it and decided to replace the valve assembly.
Today he came out to install the new valve, but told me the track adjuster won't move. He then said that he thinks the track frame is bent, preventing the track from sliding. I did not have this problem last year. I suspect there's a bump near the middle of the track rail and measuring from there it makes it look bent. So the end result was he suggested I run the machine back and forth to loosen it up.
So what I did was run the track back and forth a few times, then take a garden hose and shoot water in between the track sliders. Lots of brown water came out and eventually clear water. I then shot some oil onto the piston. Got my grease gun and pumped it. I could hear the bypass making that clocking sound, but the track adjuster moved for me and I was able to tighten the track.
It remains to be seen if the tracks stay on. I did drive the machine to another part of the lot without issue.

 

[4bz]

Something else to check for. Track rollers sometimes wear unevenly, and may have a lot of wear on only one side. You may not see the side with excessive wear if it is turned away from your angle of view (or under the track). When the worn side of the roller engages the track, you get issues with even small amounts of side pressure steering the track off the rollers. The bottom rollers are easy to check for this condition when it occurs because you can see all of the roller surface during a track adjustment. The top rollers are generally overlooked because the track is laying across the top of the rollers when the carriage is raised off the ground. A long board can usually be used to wedge the track up high enough to allow the top rollers to turn for inspection. If more than one roller is worn more on one side they can also cause randomly changing track tension as the worn rollers take up and then release the adjustment in the track.

 

[Mark A Weiss]

The mechanic installed new top rollers, as the originals were so far gone they were off the bearings, literally tilted inward toward ground on the inner side of the track. So hopefully that's not an issue anymore.
I am a bit concerned that the track adjuster is difficult to move. I was able to tension the track this time, but given that the other side had to have a new track adjuster 2 years ago, I'm thinking this side could be seizing up. I tried to get as much oil as possible onto the piston, in the hopes that some of that oil will get into the seal of the adjuster and prevent from further sticking.

 

[Legdoc]

This is my take and I must point out my OCD. Knowing the cost of an undercarriage I would consider the following. Double check the "new" tracks properly fit the bottom rollers, idlers and sprockets. Since there is an issue with the adjuster travel I would jack up the machine, block it and remove the tracks. Then thoroughly inspect all rollers and the mechanisms. I know it's a lot of work but in my experience trying to cut corners has always bit me in the azz. This is assuming you plan to keep the machine. Just my thoughts for what it's worth.

 

[Mark A Weiss]

My mechanic supposedly did a full inspection. He declared that someone recently did the undercarriage, because the lower rollers are all spinning smoothly. It was the uppers that were obviously never replaced and they were tilted due to the bearings being completely gone.
Since the heart attack and at my age, I'm past the point where I can wrestle with 900lb tracks. At this point, I'm going to change the oil in the final drives myself and grease the machine and pray nothing else major goes on it until I decide to sell.