Do tractors adhere to GVW ratings?

[CobyRupert]

Isn't the weight that the rear axle would carry due to the tractor weight and the three point hitch capacity a small fraction of what that axle might experience if it's pulling a full horsepower and the tire lugs are really hooking up?

 

[MHarryE]

Isn't the weight that the rear axle would carry due to the tractor weight and the three point hitch capacity a small fraction of what that axle might experience if it's pulling a full horsepower and the tire lugs are really hooking up?

No, it isn't. Our largest tractor is a JD 7720. In the Nebraska tractor test the maximum drawbar pull achieved with a fully ballasted tractor was 20,600 pounds pull at 20,200 pounds ballasted weight. They test on concrete and were limited by wheel hop - the tractor bouncing - at max pull. The gear they used is so low that we can't begin to use it in the field for pulling purposes - 3rd gear, very slow speed. When hooked up the best in optimum ground conditions we will easily spin all 4 wheels in 12th for which max pull is 7700 pounds. Pull will be much lower than vertical except with tracks.

 

[RedNeckRacin]

I would tend to believe that if your using the 3pt and a draft implement, lets say a plow, that you could see a lot more weight on the axle than just the static weight of the tractor and implement because of the design of the hitch.

 

[CobyRupert]

No, it isn't. Our largest tractor is a JD 7720. In the Nebraska tractor test the maximum drawbar pull achieved with a fully ballasted tractor was 20,600 pounds pull at 20,200 pounds ballasted weight. They test on concrete and were limited by wheel hop - the tractor bouncing - at max pull. The gear they used is so low that we can't begin to use it in the field for pulling purposes - 3rd gear, very slow speed. When hooked up the best in optimum ground conditions we will easily spin all 4 wheels in 12th for which max pull is 7700 pounds. Pull will be much lower than vertical except with tracks.

Very interesting.
I've always watched tractor pulls my whole life, where an older tractor (say a 3800 lb Farmall H) might hang a few thousand pounds of weight on the back to bump up into the next weight class, the older tractors pull in lower gear and the tires can really hook up on that clay track, you can see the tires actually ripple/buckle under the strain and the tractor pulls until it stalls (i.e. little or no wheel spin). As far as the OP's original concern, I've never seen a tractor break an axle.

 

[TSO]

So here is the spec page for my tractor (1648). You can see all of the rated numbers.

Also, in case my lift numbers are considered for factoring these numbers ... my 3pt lift is 3,480 lbs @ ball ends, 3084 lbs @ 24" aft. My loader lift is 2527 lbs @ full height.