Farmboy, I agree with you.
Junior, what you need to do is take a tape measure a pencil and paper to your Cat dealer or a job site that has a big Cat high drive dozer.
You need to draw out all the wheels in the configuration that you see in front of you. And then add the dimensions that you measure. Also notice where the main pivot is for the track frame. The next thing to do is get a brochure on that tractor. One of the things you will want to do is find the ratio between the distance from the center of the pivot to the centers of the front and rear idlers. So when you look at what half the tractive effort is on the spec sheet in low gear you know that it is approximatly what is being pulled on that rear idler in a hard push say its a huge rock, and you have 100% traction and the tracks are not slipping. What is happening is not only is this pull on that idler what causes the wear pattern on the rails, it is also pulling down on the final drive assembly, and up on the rear of the track frame which will tend to lift it. You ask so what? Well not only are these stresses on these items, as well as lifting the rear of the track frame and pivots the front part down, which is probably the reason a guy on here mentioned that a conventional oval dozer ripped better, but these stresses also sap horse power. There is that extra wheel to have to turn. There is like a major tug a war going on between that high final and that track frame.
Now look at the oval type drive on the old D9G and H. If there is a blade mounted and you are pushing, all that force is transmitted to the final support bearings and no tug a war pulling down on the final or frame of the tractor or track frame. The sprocket pulls straight on the track, there is no lifting in the rear and no extra wheel to pull the chain over. But with the newer free planetary finals on the ovals there is pulling and stressing the mainframe. With the dimensions and spec sheet you can calculate the amount of lift up and stress where that track chain rail meets the rear idler,
it amounts to way more per unit loading that at anyother roller that the chain makes contact with. This is why the high drives eat track chain at a faster rate than the ovals do. And may brand loyal ones will argue it.
But like farmboy says, Cat sales really pushed how great the hi drive was, but now they are going back to the ovals. I have always wondered why the D3's never became a hi drive. I think cat sees the goof they did, and how Komatsu and John Deer and others are taking away sales. Just like the old cletracs, someday these hidrives will be museum pieces.
