Axle ratings where is the weak link?

This topic got me to researching my own axle ratings.
I found this telling comment on quality gear.com's site, among others:
"The Dana 80 has a gross weight rating up to 11,000 lbs, however it is common practice among manufacturers to derate Dana 80's. Gross axle weight ratings are lowered by the vehicle manufacturer for safety and tire reasons."
Notice is says, "up to 11,000". The fact is the strength of the housing, the size and stoutness of the RGP, the bearing size and number, and finally strength and spline count of the axle shafts that have to do with weight rating.
I think i have the highest rated 35 spline, Dana 80...until I crawl under a MoHo with a Dana 80 with 37 spline axle shafts rated at 13K pounds GAWR. I don't know what the differences are with the internals. Spline count means strength.
My front Dana 60, which has been drastically upgraded, still has only a 6000 pound or 6500 pound rating depending on whether it resides in a Ford or a Ram. With so many Dana 70 parts, which can have a front axle rating up to 8K pounds, what is it?, a Dana 65? There is no actual published rating on this hybrid axle, only a large scale upgrade in strength of the parts into an unpublished higher strength. Now the RGP, just about the only leftover besides the housing is probably the weak part. It's been my experience building rock crawlers that you just pull on that string and find out where it breaks and upgrade that part.
I notice the 11.5" AAM axle used by almost all truck mfgrs after about 2003 have a slightly larger RGP than the Dana's, but only a 30 spline axle, similar to the 1990's Dana 70 and 80. Around 2000 was the first year they offered the 35 spline D-80 in Fords and Dodges. Only the highest rated Dana 80 had the 37 spline axle shafts.
jefe

54suds wrote:
for what its worth here's some inter net info :


rupprider wrote:

Evidently there are two models of 14-bolt, one has a 10.5 inch ring gear, and one has a 11.5 inch ring gear.

That is correct. In GM 2500HD trucks, the 6.0L gas models got the 10.5" ring gear axle. The Duramax and 8.1L trucks got the 11.5" axle.

And yes, AAM rates the 10.5" axle for 8600# and the 11.5" for 10,000#


KJ

Can you provide us the link??

No actually I'm saying the opposite. Yes the new Rams are stout as heck,but so is your truck sitting in your driveway. You get a new ram gasser and you're setting camper on the exact same axle and similar frame.

I'm saying your 4wd diesel is carrying the bulk of the 4wd and engine up front, which is artificially lowering the payload to magically sum up to the gvw......which is also low for that model truck.
What I'm saying is the devil is in the gvw class rating numbers which have summarily gone up over the last several years, some on trucks with no significant changes.
Go buy a new 2wd reg cab gasser Ram to get that magic 7klb payload rating, but the truck you have has the same equipment to haul waaay more than 4000lbs.

For those who can quote every spec for both trucks, I'm not insinuating that the 2 trucks above have the same real world payload capacity. What I'm saying is there is not a 3klb difference between the 2 once you get past the semantics and start comparing piece by piece.

Grit dog wrote:
Devo, lots of good info here and it appears you've honed in on the limit. Right around 10klbs on the rear axle.
I wouldn't want to go any more than that on the current/recent crop of 1 ton trucks for sure. I'm running right about 8klbs on my "overloaded" truck with the same chassis configuration and the rear diff is very happy. Tested by the redneck temp gauge (see how hot the rear end is after a good long loaded run).
One thing to note that has been explained many times and seems to be going around you, is what the ratings are based off of.
You talk about going to a 2wd gasser to gain payload. Yes on paper and within class limit general gvw limits this helps your cause, but a 2wd gasser saves virtually nothing when it comes to rear axle loads. Also, for GM and Ram, as they're applicable to your current truck, they use the EXACT same rear axle as your 07 and most all 2500/3500 variations since the early 2000s. Exception being the newer Ram duallys run a slightly heavier axle, in that the ring gear is slightly larger. Unsure of the actual rated capacities but it's the same basic axle, not a large step up in capability.
The point for you to consider is that aside from going to a class 4 or 5 truck, regardless of what new or newer dually you choose that has better payload on paper, that additional payload is largely a numbers shuffle (like now duallys magically have a 14kgvw limit, when trucks on the same chassis used to have lower gvws a few years back.
This is all considering apples to apples wheelbase/cab configurations as that is what will have a real effect on empty rear axle loads and weight bias front to rear.

Thanks Grit dog
the configuration I am looking at is 14k gvwr , I think the rawr is 9700 and a payload of 7k camper rating of close to 5900 compared to what I have now at 11400 gvwr 8200 rawr payload of 4000 and a camper rating of 3059 so no matter what the gasser should handle the most on paper , the ram trucks have the best numbers on paper. I get it that the rear axle doesn't carry the whole load of the higher gvwr' s
Mike

Devo, lots of good info here and it appears you've honed in on the limit. Right around 10klbs on the rear axle.
I wouldn't want to go any more than that on the current/recent crop of 1 ton trucks for sure. I'm running right about 8klbs on my "overloaded" truck with the same chassis configuration and the rear diff is very happy. Tested by the redneck temp gauge (see how hot the rear end is after a good long loaded run).
One thing to note that has been explained many times and seems to be going around you, is what the ratings are based off of.
You talk about going to a 2wd gasser to gain payload. Yes on paper and within class limit general gvw limits this helps your cause, but a 2wd gasser saves virtually nothing when it comes to rear axle loads. Also, for GM and Ram, as they're applicable to your current truck, they use the EXACT same rear axle as your 07 and most all 2500/3500 variations since the early 2000s. Exception being the newer Ram duallys run a slightly heavier axle, in that the ring gear is slightly larger. Unsure of the actual rated capacities but it's the same basic axle, not a large step up in capability.
The point for you to consider is that aside from going to a class 4 or 5 truck, regardless of what new or newer dually you choose that has better payload on paper, that additional payload is largely a numbers shuffle (like now duallys magically have a 14kgvw limit, when trucks on the same chassis used to have lower gvws a few years back.
This is all considering apples to apples wheelbase/cab configurations as that is what will have a real effect on empty rear axle loads and weight bias front to rear.

In our case the additional weight on the front axle only increased by slightly over 100 lbs after loading and weighing the TC.
I think this is a common finding on here for many.
Center of gravity makes the difference here, even a couple of inches ahead of the rear axle is desirable.
A concern that I have with pushing the RAWR are the bearings and seals is that a factor taken into consideration by the manufacturers when determining ratings?

In a nutshell, the ratings are so low because the manufacturers KNOW people will go "full re tard" (using Grit Dog's words) on the truck, believing that they are well within all the ratings. People have no idea what things weigh, and no easy access to weigh stations. Even if they did, and found they were grossly overloaded, they'd just conclude that the manufacturer was full of "it" and continue to abuse the truck. Truck drove them there "just fine" after all.

The manufacturer wants the truck to handle it until the warranty's up, because if it doesn't, it's money out of the manufacturer's pocket. Trying to play "weight police" to deny warranty claims is a can of worms they don't want to open.

just and FYI almost all the weight of the TC rests on the rear axel very little weight goes to the front

Thanks for the help , I am not trying to get around any laws or restrictions I am just trying to remain safe while making this move to a TC and not buy a new truck if I can safely handle one of the models of TC's we are looking at and our stuff . I over stated my tire capacity in the original question it is actually 2470 per tire with dual wheels with the original stock tire size and steel rims so it is like 9880 which seems closer to the axle rating . If I am understanding this correctly upgrading the tires would then shift the weak link back to the 10k axle( manufacturer rating not GM ). I also looked at some weight slips from when I first stared towing with this setup and there is very little room left on the Front axle by the rating . I am guessing because of the weight of the diesel and the 4x4 , Not sure how much weight transfers to the front axle with a TC but there is not much weight left in the front of my current trucks axle . I am coming to the realization that as well as my current truck tows my fifth wheel it is not going to be a good fit for a large truck camper I guess I picked the wrong model year for weight ratings . I willl be looking at a gas 2x2 DRW Crew cab like I asked about in another post when asked the big question gas vs diesel but for us not towing anything gas will be fine , from what I have read . I will just have to learn to live with a gas motor after 10 years with the diesel , and the 2x2 which should not be a big deal either since we are not planning to be off road and have used the 4x4 once on wet grass with the trailer in 10 years and don't use the truck in the winter months here in New England. Thank you all again for all the help and replies it is much appreciated . As I wrote in the other posts we are trying to get this right the first time unlike having had three trucks and three trailers before finding to right setup that has worked for us for the last 8 years but is now too big for what we want to do in retirement.
Mike