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Old 04-27-2012, 07:34 PM   #1
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Default Axle weight capacity (GAWR)

I hope this will become a discussion thread, where we can gather info, and post up solutions and improvements related to the rear axle of our Class B RVs.

I will come back to this first post, and add data, as it becomes available.

Gross Axle Weight Rating (GAWR).
Different axles have different GAWR's. From light duty cars up to huge military vehicles and earth movers.
Our Class B RVs typically have an axle for a 3/4 Ton or 1 Ton application.

First data point is:

From WikipediA:

Dana 60
Manufactured in both full float and semi float variations. The semi float axles have GAWR up to 5,500 lbs and the full float axles were rated up to 6,500 lbs.


Info from Booster:
The Dana 60 in the Chevy Roadtreks is actually a Dana Super 60 semi-floater. As near as I have been able to find out, the main differences are two extra bolts in a beefier rear cover (12 bolts compared to 10) to make it more structural, and bigger tubes and wheel bearings. Maybe some other internals, but hard to say.

The information on actual axle maximum load is very hard to find and sketchy, but it looks like most are saying right around 6K pounds, so the 6082# on the Chevy rating plate is pretty close and is equal to the tire maximum rating.
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Old 04-27-2012, 07:35 PM   #2
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Default Re: Axle weight capacity (GAWR)

Gross Axle Weight Rating (GAWR).
Different axles have different GAWR's. From light duty cars up to huge military vehicles and earth movers.
Our Class B RVs typically have an axle for a 3/4 Ton or 1 Ton application.

In this group, there are Semi-Floating and Full-Floating axles.
Visually, the semi floating axle, is almost flush, across the wheel mounting surface.



The full-floating axle, has a large hub protruding from the middle of the wheel mounting surface.


The full-floating axles almost always have a higher GAWR than the semi-floaters.

Ours R/T 190, Chevy Express 3500, has a semi-floating axle, that I believe is a Dana 60 (need to confirm).


From WikipediA:

Dana 60
Manufactured in both full float and semi float variations. The semi float axles have GAWR up to 5,500 lbs and the full float axles were rated up to 6,500 lbs.


5500 pounds!!! Is that all???

At 5400# on the rear axle, our R/T is nearly at full axle capacity of 5500#. It is over the spring capacity of 4970#.

Does anyone have any other info on the rear GAWR for these Class B RV's? There is a tag in the driver's door jam, that may say what the front & rear GAWR is for your rig.
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Old 04-27-2012, 08:25 PM   #3
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Default Re: Axle weight capacity (GAWR)

I think that if you got the optional transmission cooler/limited slip option it was a beefier rear end, but not certain. Ours is just like yours.
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Old 04-28-2012, 10:25 PM   #4
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Default Re: Axle weight capacity (GAWR)

I looked at the door stickers on our van today, and both the Roadtrek sticker and the Chevy sticker list the rear axle capacity at 6084#, and we have a semi-floater. The 6084 is the max tire capacity, so the actual rear end maximum could be more.
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Old 04-30-2012, 06:43 PM   #5
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Default Re: Axle weight capacity (GAWR)

I took a couple photos of the markings on the differential housing. The axle in our fan is definitely a Dana 60. Most of the info I can find out about the Dana axles show the 60 will have a casting number of "60" or "248".

This is where to look on a Dana axle, for the various markings.


This is not an easy spot to see, under a Roadtrek. The generator gets in the way. The photo below shows the view from under the generator, looking forward, at the rear axle. You can see the casting number on the casting. The tube in the upper left is the generator exhaust. The tube at the bottom is the sway bar we added.


A closer view of this casting number shows it to be "248"


As posted earlier, the Dana 60, with a Semi-Floating axle, has a GAWR of 5500 pounds. If it were a Full-Floating axle, the GAWR would be 6500 pounds.

Now I need to check my door sticker, and see what it says.
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Old 03-21-2015, 07:17 PM   #6
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Default Re: Axle weight capacity (GAWR)

I ran across this thread when I was looking for information as to what axle Roadtrek uses when you get the trailer towing package. I still don't know what they use, however, but can shed a little light on some of the questions in this discussion, as we have been looking at an axle swap.

The Dana 60 in the Chevy Roadtreks is actually a Dana Super 60 semi-floater. As near as I have been able to find out, the main differences are two extra bolts in a beefier rear cover (12 bolts compared to 10) to make it more structural, and bigger tubes and wheel bearings. Maybe some other internals, but hard to say.

The information on actual axle maximum load is very hard to find and sketchy, but it looks like most are saying right around 6K pounds, so the 6082# on the Chevy rating plate is pretty close and is equal to the tire maximum rating.

We hear of failures, but not all that many, I think, so they are getting by with the axle, although it was originally beefed up to take it from a 1/2 ton axle to a 3/4 ton axle, and is now on fully loaded 1 tons. The wrong offset wheels, if you have them, also put more load on the wheel and carrier bearings. Again, though, less failures than I would expect----except for us and some other 2007 vintage folks I have read about. There was likely a bad run of the big cast housings in that time frame, which caused early failures. Ours was rebuilt by GM at 5600 miles with all new guts, including gearset. We are now at 27K miles and it is getting a little noisy when the power is on. I wasn't all that concerned right away because all rear drives whine a little here and there, but when I had it in to be aligned, the tech drove it and said he thought the pinion bearings were going, or were loose, because it whined at all speeds when accelerating. I took it to a couple driveline guys and they said the same (as does the factory manual). They said if it were only at particular speeds, it would not be bad, but at all speeds probably is. Didn't know that. The oil is staying clean, so it is not at immanent death mode, but not pristine either. We have been kind of paranoid after the first failure so early, and that other 2007s that I have heard about got rebuilt twice under warranty, failed again and were replaced with a complete axle, housing and all, that finally fixed them permanently.

As near as I have been able to find out, GM used three axles in the one tons. The Dana Super 60 semi-floater 9.75" ring gear, the Dana Super 70 full floater 10.5" ring gear, and probably an American Axle (often called GM corporate) full floater, 11.25" ring gear (I have not been able to actually find one, though, and it may only be on cutaways). It may also be a Dana 80 in the 11.25".

Our fear is that we will have a failure on the road, and have to put $1500+ in the one we have, and it will probably still fail again besides. Since we have higher capacity tires and suspension, it made sense to look at getting the axle capacity up also, rather than just getting another Super 60 to put in complete. Most sources I found put the capacity of the Dana Super 70 at about 7500#, so that looked pretty good to me. The driveline guys I talked to all said that at 6000# load, you should not be on a sem-floater, and didn't really have much bad to say about the Super 70. The did prefer the 10.5" GM corporate that was used in previous models, for some nice features and aftermarket parts availability, but said both were extremely durable in a one ton.

When I started looking for a used, complete Super 70 with 4.10 gears, it became obvious they are a bit rare, and at least 50% more cost than the 3.73 versions in most cases. There is a carrier gear split at 4.10, so if you get a 3.73 and try to change gears, you can just put in a rear gear and pinion set. That wouldn't be bad, if you were going to add a posi unit you would need to change the carrier also, but it turns out there are no real "streetable" posi units for the Dana's in the aftermarket. All that you can get are the old plate clutch, always engaged, units that are so wicked scary on the slippery roads, or a very expensive air, electric, or cable locker. What is very interesting is that GM put auto lockup differentials into the Dana differentials. That lockup differential is made for them by Spicer, but you can't buy them outright. If you have one, you can get service parts from GM for them. Long story short, searched for a Dana Super 70, 4.10 gears, with the GM posi, which is really an auto locker called Gov-lock and only engages when you need it, and never about 20mph, so it very safe for the street.

It is interesting the most of the Dana 70s I found were cheaper than the Dana 60s, so they must sell few 70s and lots of 60s, which makes sense.

We now have one on the way that will get here in about a week. 84K miles on it out of a 2004. I don't have the setting tools and bearing and seal drivers for this style, so will take it in to have new seals, bearing inspection, and setup check. At 84K everyone said the bearings and gearset should be fine and good for 200K more minimum, so we will see, but it 10 year old, so seals are for sure.

Indications are that it is close to a drop in, although a very heavy one. It will need different rotors to clear the big floater hubs, but the driveshaft is listed as the same on the interchange charts, so we will see. Might need different u-joints, but couldn't find that out. All the other brake parts look to move right over.

Hopefully, this will put our insecurities to rest about recurring issues, and maybe the locker will make us a bit more mobile around the beaches and forests.
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Old 03-21-2015, 09:19 PM   #7
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Default Re: Axle weight capacity (GAWR)

Way beyond my skill set

So you have a Dana Super 70, 4.10 gears, with GM posi-traction on the way? I think you've wanted to do this upgrade for a while.

The '04 RT we owned had the 4.10 ratio, locking differential & external transmission cooler. I have no idea what axle was used. Maybe someone with the tow package option will see this topic and post the info for future reference.
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Old 03-21-2015, 09:27 PM   #8
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Default Re: Axle weight capacity (GAWR)

Quote:
Originally Posted by markopolo
Way beyond my skill set

So you have a Dana Super 70, 4.10 gears, with GM posi-traction on the way? I think you've wanted to do this upgrade for a while.

The '04 RT we owned had the 4.10 ratio, locking differential & external transmission cooler. I have no idea what axle was used. Maybe someone with the tow package option will see this topic and post the info for future reference.
It sounds like the 04 you had was a towing package Roadtrek, as the posi and cooler were what made it so. Do you recall if it was a full floater?
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Old 03-21-2015, 09:41 PM   #9
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Default Re: Axle weight capacity (GAWR)

Sorry, don't know. I didn't know the difference between full & semi floater back then.
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Old 03-22-2015, 01:51 AM   #10
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Default Re: Axle weight capacity (GAWR)

These guys make parts for the dana 60/S 60 that are darn near bulletproof. The S 60 is a Dana 60 manufactured by Strange Engineering.

http://www.strangeengineering.net/high- ... nents.html

Many of them are limited slip, and they also sell gears too. Or if you want to spend, you can buy a complete unit.

http://www.quadratec.com/ also sells differential parts too. Yes they are designed for Jeeps, but many parts will work in the Dana 60.

One thing that you haven't touched on yet though. You could upgrade your suspension, but the data plate still retains the old info. If you got pulled over and ordered to go to a scale they would fail you because they use the data plate info. It is possible to get a new data plate, but you'd have to pay to have the vehicle certified for that new weight. From what I understand this is different in the US and maybe other parts of Canada, I can only speak about Manitoba.

You should also upgrade brakes and tires if you were going to increase your GAWR/GVWR.
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