rear axle rating

Highway system is 34K on tandem, some roads in Colorado let you go to 36k.
Why buy 40K, because it is good to have higher rated axles if you need them, or the time you do run 1500 over on drives it is safer, and easier on equipment.
Upgrading is a lot more complicated then just replacing breaks, and tires.
Rims, springs (bags/air beam), bolts, etc, etc.

 

46k lb rears are heavier all around. Better housings, beefier internals, stronger suspension etc. Handle pulling heavier weight better too without burning up. Out here in western Canada axle weight limits are higher than the US so its much more common to see 46k rears as a standard spec.

 

True about 46k out west, but you have to watch out for your tare (curb) weight. On some trucks 46k rears also mean the frame is doubled, along with beefier running gears and diffs. My last large car tared at 23,245 lbs. Not so bad running north of the border, because tandems can be 84k gvw, and tridems 102,400 gvw. You have some room. But with everybody trying to cram 46k to 48k into tandems now, you won't be able to run in the States with that tare weight.

 

Some guys run over weight permit loads. Back in the day (actually not that long ago lol) Some of us run over weight loads with out the permit b4 they started keeping a score card on us.

 

A tractor is built with a certain rating, for strength.

There are times it is necessary, sometimes not always smart to push it or exceed it.

I took a load onto a mack offset cab once that was made in the 60's you probably had about a 38000 pound rating on that truck. Unfortunately the gross weight is theoretical when a particular state scale failed at 134700. After a truck breaking load like that, the tractor was totaled. We never saw it again. It actually became unsafe beyond 28 mph when the front end fell down and the steering went out so we went no faster than 20. You would not get much more than that anyway. It was a very bad day in my life time. I hauled many heavy loads under a permit and usually had strong tractors to do the job. But not always. They simply get totaled.

Fast forward to 2001, our Century was rated at 42000 which provided a nice margin of safety from time to time when the drives were a touch heavy.

 

Another problem people don't know is a lot of the tractor axles are to thin. They flex under a load a you get bad tire wear and you can't ever figure out why. They say if look on the axle housing on the top it stamped how thick it is. 9 to thin and 11 is what you want to see.

 

Axles will take maybe 9 ton. Not much more than that each.

You can build a axle to take a 50 ton load, but you will find you need a 1500 horse battle tank turbine to use the #### thing LOLZ.

 

Min

Mine are stamped 12.7 , yes they are 46,000 lbs rears.

 

Besides weight carrying capacity, the main reason for heavier rear axles is they have a much higher pulling capacity.
40k axles usually top out at 110,000 lbs gvwr or less.
My 46k are rated to 185,000 lbs gvwr. I actually pull 140,000
I have pulled 140,000 with standard 40kaxles, but they ran really hot and failed after only two years. The 46k axles hardly get warm at all.