Consider this.
The 600 Series tractor/loader/backhoe uses the same trans-axle housing as the current crop of Eastman tractors in the 3000 and 4000 Series. The trans-axle is also the same as the one used on the 200 and 400 Series tractors since 1969 except for some added gusseting to the casting.
The Davis backhoe used on the 600's likely weighed in at over 1000 LBS and then.....there was a hefty subframe plus a pretty large counterweight up front that likely added another 400 LBS. Granted, the superior front axle/wheel assembly handled a portion of this weight but not that much. Most of it was concentrated on the back end. Yes.... the backhoe used a thinner axle bushing to allow a larger diameter axle shaft but most of the reasoning behind that, had to do with the extended axle shafts that held the floatation rim/tire combo.
If you go to the HOME PAGE and click on the HISTORY link and then the Attachments section at the bottom, check out the 190 with the chain trencher and also keep in mind Steve Guider's 190 with the forklift conversion.
All of these things demonstrate just how robust the trans-axle is.
Adding weight to the tractor is literally a balancing act. On a 200 or 400 model, you could add 1000 LBS but....... could you add that much weight in just one spot? The answer is no. If you tried to put it all just behind the rear axle, the front wheels would come off the ground. Therefore, you must add the weight judiciously so that the steering control is maintained and that the tractor is not unbalanced or unsafe. Secondly , there is no point in adding weight for the sake of adding weight. Bragging rights are not at issue. Weight is added until the tractor does what you want it to do. Any weight beyond that point is unnecessary.
Obviously, tire loading and wheel weights do nothing to change the way a tractor steers and in my opinion, those two options should be tackled first. If the tractor is still found wanting for traction, then weight behind the axle, as close in as possible, is the next method to take on. Building a method of attaching loose weights that are easily handled is ideal. The tractor can then be adjusted quickly for various tasks.