450 track "snap"

[little1406]

My 1968 JD450 does not seem to have very loose tracks. They barely sag between roller and sprocket on top. However, under some circumstances when turning I seem to get the track to ride up onto the flanges on the bottom rollers for a bit. When it falls back into place, there's a loud snap or bang that shudders the whole machine.....not a nice feeling. Otherwise the machine works pretty well. This does not happen a lot, just once in a while, mainly on uneven ground when turning.

Is this track behavior somewhat normal? totally abnormal? a sign of impending doom?

Any advice would be greatly appreciated.

[jtrichard]

are you sure its climbing the rollers? or you could be getting rocks in between the chain/sprocket its sounds just like what you describe is happening and it generally happens when turning

[little1406]

I'm not sure it's climbing the rollers but I am sure it's not rocks. I can't find a rock on this place. We do a lot of fencing and drill down 3.5' with a soil auger and I have yet to encounter a single rock. It's all fine sand and clay.

[vestor_guy]

Just riding up on the rollers should not produce a loud snap but if it does ride up on the rollers due to worn flanges, the sprokets may be "catching" on the chain. That would produce a LOUD snap.

Take a look at the condition of the front idlers, rollers and sprokets. Several photos would help.

[vestor_guy]

On a dozer, the most common roller to fail is the rear one. On a loader, it is the front one. Look at your rear roller on the side where the loud noise is heard.

[KenP]

deleted

[Farmerford]

I am with vestor_guy; when you brake to turn the slack in the inside track bunches up between the rear roller and sprocket. The sidewise motion of the rear of the machine toward the outside of the turn can move the track enough that the chain hangs on the edge of the sprocket teeth. If you check the side of the sprocket teeth you may see signs of the chain hanging.

[LeonardL]

Have you inspected the shock springs on your track frames? Usually the culprit here is the adjusting bolt on these springs. They will break or the nuts will back off and cause the springs to fully extend or at least try to extend. Then while turning, this will force the springs rearward and then when you stop turning it releases this spring tension and you will get a very loud bang or a slap as it forces everything back forward. It also tends to want to jerk the machine around causing this shudder you spoke of. Rollers and climbing tracks typically don't make the machine do this. If it is riding up on the rollers or if you have a bad roller usually you track tension will sag a little, not tighten up. The noise they make is different and will make the noise no matter if you are turning or not. The fact that you say you don't have any slack in your track makes me suspect these springs or at least one of them is trying to fully extend. I'm not saying you shouldn't look at these other things the guys have pointed out. You should inspect the entire track system from top to bottom. You may well have more than one issue going on.

[little1406]

Thanks for the suggestions.....

I'll report back when I've studied the thing a bit more.

I didn't even know there was a spring in there.....I'm reading about it in the service manual now.

[tomcat4144]

i agree with the others. it is the sprocket riding up on the chain. i had the same thing happen on a everything new undercarriage. undercarriage just not quite aligned enough and sprocket would ride up the chain and "snap" back on. just a few washers on the track carriage was enough to pull it back in center. this was the sprocket riding up the outside of the chain.