2500 vs 3500 axles

[UglyViking]

I'm curious about the difference between the 2500 and 3500 axles. I looked at the spec sheets and saw that the GAWR for the rears seem to either be listed as 6k or 7k depending on if it's a 2500 or 3500. I know previously that the GAWR included the full suspension and brake system. I'm not sure if that is still the case or not but my understanding is the only difference between the two is coil vs leaf. I also believe that the AAM axle is identical between the two, but it made me think, is that the case?

I am curious if anyone knows if there is a difference between the two axles, outside of the leaf vs coil.

 

[agtcovert]

I'm curious about the difference between the 2500 and 3500 axles. I looked at the spec sheets and saw that the GAWR for the rears seem to either be listed as 6k or 7k depending on if it's a 2500 or 3500. I know previously that the GAWR included the full suspension and brake system. I'm not sure if that is still the case or not but my understanding is the only difference between the two is coil vs leaf. I also believe that the AAM axle is identical between the two, but it made me think, is that the case?

I am curious if anyone knows if there is a difference between the two axles, outside of the leaf vs coil.

The SRW HO I have on order lists a 12" vs 11.50" AAM. There's a minor difference (maybe in the ring and pinion size?). If I recall, a 3500 SO had the smaller 11.50.

So, sorry I can't give more specifics. Hopefully someone knowledgeable can chime in. But I do know there's a minor difference depending on how you spec.

 

[JohnnyC]

I'm curious about the difference between the 2500 and 3500 axles. I looked at the spec sheets and saw that the GAWR for the rears seem to either be listed as 6k or 7k depending on if it's a 2500 or 3500. I know previously that the GAWR included the full suspension and brake system. I'm not sure if that is still the case or not but my understanding is the only difference between the two is coil vs leaf. I also believe that the AAM axle is identical between the two, but it made me think, is that the case?

I am curious if anyone knows if there is a difference between the two axles, outside of the leaf vs coil.

HO's have 12" AAM vs 11.5" for the SO's. Brakes and axle tubes are also larger than the SO 3500's. I had same questions and found answers here: https://hdrams.com/forum/index.php?threads/max-tow-package.274/page-2

 

[UglyViking]

So I get the HO having a larger diameter axle housing, if I recall the HO trucks also have a different transfer case due to how the Aisin trans mounts up. The thing that is interesting is that, at least according to the FCA towing docs, the SRW trucks all have an identical 7k rear axle rating. I looked at the 68RFE and Aisin and while I don't doubt that the axle is a different diameter, and maybe has different brakes, it seems that the axle rating is the same?



So perhaps this listing is without the max tow package, or similar options, and that is another question.

My primary question is, it seems like the 2500 and 3500s have the same rear axle on the non-HO trucks. If that is true then the rear ends on the 2500 and 3500 trucks are identical with the single exception of the coil vs leaf thing. If that is also true, then that means that the GAWR is incorporating the braking system and suspension into the GAWR.

I'm just curious on this overall.

 

[agtcovert]

I found this: 2019 Specs

Edit: 2021 Specs

It does note a different transfer case for the HO. I couldn't find anything on GAWR differences, nor did I see anything indicating brake size differences on the 12" axle. It's interesting the 2019 specs show the 12" on max tow; my 2022 build sheet for an SRW lists the 12", and I know there's no max tow option (at least that I selected). I wonder if that changed with the 2021 HP/TQ increases.

 

[H3LZSN1P3R]

So I get the HO having a larger diameter axle housing, if I recall the HO trucks also have a different transfer case due to how the Aisin trans mounts up. The thing that is interesting is that, at least according to the FCA towing docs, the SRW trucks all have an identical 7k rear axle rating. I looked at the 68RFE and Aisin and while I don't doubt that the axle is a different diameter, and maybe has different brakes, it seems that the axle rating is the same?

View attachment 21826

So perhaps this listing is without the max tow package, or similar options, and that is another question.

My primary question is, it seems like the 2500 and 3500s have the same rear axle on the non-HO trucks. If that is true then the rear ends on the 2500 and 3500 trucks are identical with the single exception of the coil vs leaf thing. If that is also true, then that means that the GAWR is incorporating the braking system and suspension into the GAWR.

I'm just curious on this overall.

My neighbor has the 19 hemi 3500 with a 7k rear axle

 

[brian.holtmann]

So I get the HO having a larger diameter axle housing, if I recall the HO trucks also have a different transfer case due to how the Aisin trans mounts up. The thing that is interesting is that, at least according to the FCA towing docs, the SRW trucks all have an identical 7k rear axle rating. I looked at the 68RFE and Aisin and while I don't doubt that the axle is a different diameter, and maybe has different brakes, it seems that the axle rating is the same?

View attachment 21826

So perhaps this listing is without the max tow package, or similar options, and that is another question.

My primary question is, it seems like the 2500 and 3500s have the same rear axle on the non-HO trucks. If that is true then the rear ends on the 2500 and 3500 trucks are identical with the single exception of the coil vs leaf thing. If that is also true, then that means that the GAWR is incorporating the braking system and suspension into the GAWR.

I'm just curious on this overall.

I would agree as I just compared 2 VINs Build Sheet from very similar optioned 21 Big Horn SRW 2500 and 3500 and they look the same 6000 on front 7000 on rear and 11.5” rear end.


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[UglyViking]

My neighbor has the 19 hemi 3500 with a 7k rear axle

Makes sense, the spec sheet seems to list all the 3500s with a 7k rear axle.

I would agree as I just compared 2 VINs Build Sheet from very similar optioned 21 Big Horn SRW 2500 and 3500 and they look the same 6000 on front 7000 on rear and 11.5” rear end.


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Interesting… Do you have links/screen shots you can share of that? I've not yet seen a 2500 with a 7k rear axle, I wonder if FCA updated the 21+ trucks to all have the 7k axle for simplicity, but if that is the case it may be that I'm incorrect in my assumption that the GAWR includes the suspension.

 

[brian.holtmann]

Makes sense, the spec sheet seems to list all the 3500s with a 7k rear axle.


Interesting… Do you have links/screen shots you can share of that? I've not yet seen a 2500 with a 7k rear axle, I wonder if FCA updated the 21+ trucks to all have the 7k axle for simplicity, but if that is the case it may be that I'm incorrect in my assumption that the GAWR includes the suspension.

Sorry, I looked at it wrong same front 6000 axle and same 11.5” Single rear axle.


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[brian.holtmann]

Makes sense, the spec sheet seems to list all the 3500s with a 7k rear axle.


Interesting… Do you have links/screen shots you can share of that? I've not yet seen a 2500 with a 7k rear axle, I wonder if FCA updated the 21+ trucks to all have the 7k axle for simplicity, but if that is the case it may be that I'm incorrect in my assumption that the GAWR includes the suspension.

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[UglyViking]

@brian.holtmann ok, that makes more sense to me. So perhaps my initial thought was correct, the GAWR takes the suspension into account. I had read from other posts, not sure if here or elsewhere, that the GAWR no longer takes the suspension into account, which seemed odd but I didn't have any data to refute at that point.

If I am correct here, that means that the 11.5" rear axle is likely rated for 7k or higher across the trucks, and the 6k rating seen on the 2500 trucks is due to the coils. If so that is pretty interesting and also makes sense why I see and hear so many 2500 trucks running overloaded without failures (to be clear, I'm not recommending this).

As a total aside, it's pretty crazy to see the numbers on the DRW config, almost 10k on the rear axle alone!

 

[brian.holtmann]

@brian.holtmann ok, that makes more sense to me. So perhaps my initial thought was correct, the GAWR takes the suspension into account. I had read from other posts, not sure if here or elsewhere, that the GAWR no longer takes the suspension into account, which seemed odd but I didn't have any data to refute at that point.

If I am correct here, that means that the 11.5" rear axle is likely rated for 7k or higher across the trucks, and the 6k rating seen on the 2500 trucks is due to the coils. If so that is pretty interesting and also makes sense why I see and hear so many 2500 trucks running overloaded without failures (to be clear, I'm not recommending this).

As a total aside, it's pretty crazy to see the numbers on the DRW config, almost 10k on the rear axle alone!

I would agree totally with your synopsis unless someone has any other information to discuss.


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[H3LZSN1P3R]

@brian.holtmann ok, that makes more sense to me. So perhaps my initial thought was correct, the GAWR takes the suspension into account. I had read from other posts, not sure if here or elsewhere, that the GAWR no longer takes the suspension into account, which seemed odd but I didn't have any data to refute at that point.

If I am correct here, that means that the 11.5" rear axle is likely rated for 7k or higher across the trucks, and the 6k rating seen on the 2500 trucks is due to the coils. If so that is pretty interesting and also makes sense why I see and hear so many 2500 trucks running overloaded without failures (to be clear, I'm not recommending this).

As a total aside, it's pretty crazy to see the numbers on the DRW config, almost 10k on the rear axle alone!

No the payload is what brings the suspension in to play the axles are rated only by Rams numbers on brakes and bearings if you look at amm sites they list the 11.5 at 11000 lbs cap interestingly enough so either ram has a huge safety factor or the bearings and hubs they use cant handle the weight

 

[UglyViking]

No the payload is what brings the suspension in to play the axles are rated only by Rams numbers on brakes and bearings if you look at amm sites they list the 11.5 at 11000 lbs cap interestingly enough so either ram has a huge safety factor or the bearings and hubs they use cant handle the weight

Well brakes and bearings are identical on the 2500/3500 SRW trucks right? I know the 2500 has a lower payload than the advertised GAWR due to registration and keeping it under 10,001lbs, but even the 3500 trucks have a lower payload than what the combo of axles would be. It could be that the brakes or hubs are the limiting factor, I've got no clue, but frankly I wouldn't be surprised if FCA is adding in safety factors on top of it.

It would seem like the limiting factor (as the difference between the 2500 and 3500) isn't brakes, since both trucks share the same, and it isn't hubs, since from my understanding both trucks share the same.

I guess my point wasn't really pointing to "payload" by the legal definition. Why would it be that the 2500 and 3500 trucks use the same rear axle, but have 1k different rating on the axle then? Again, I'm assuming hubs are the same, I know the brakes are. If AAM is only making 1 version of the 11.5" (which I assume is the case) and everything else is identical, and the suspension isn't factored into the GAWR, then how is it they get two different ratings? Did FCA just lower the 2500 rear for giggles?

As an aside, for this very reason is why I find it funny when certain "tow police" talk about having a margin of safety for payload/tow numbers. AAM builds in a safety margin (prob around 2x), then FCA likely builds in a safety margin (maybe .4-.5 from the looks of it), then end users say you should keep 20-25% as a safety margin. So at the end of the dat when the truck may be more than capable of handling north of 12k on the rear axle, end users end up with 1.5k for safety.

Not looking to start that argument, just saying…

 

[H3LZSN1P3R]

Well brakes and bearings are identical on the 2500/3500 SRW trucks right? I know the 2500 has a lower payload than the advertised GAWR due to registration and keeping it under 10,001lbs, but even the 3500 trucks have a lower payload than what the combo of axles would be. It could be that the brakes or hubs are the limiting factor, I've got no clue, but frankly I wouldn't be surprised if FCA is adding in safety factors on top of it.

It would seem like the limiting factor (as the difference between the 2500 and 3500) isn't brakes, since both trucks share the same, and it isn't hubs, since from my understanding both trucks share the same.

I guess my point wasn't really pointing to "payload" by the legal definition. Why would it be that the 2500 and 3500 trucks use the same rear axle, but have 1k different rating on the axle then? Again, I'm assuming hubs are the same, I know the brakes are. If AAM is only making 1 version of the 11.5" (which I assume is the case) and everything else is identical, and the suspension isn't factored into the GAWR, then how is it they get two different ratings? Did FCA just lower the 2500 rear for giggles?

As an aside, for this very reason is why I find it funny when certain "tow police" talk about having a margin of safety for payload/tow numbers. AAM builds in a safety margin (prob around 2x), then FCA likely builds in a safety margin (maybe .4-.5 from the looks of it), then end users say you should keep 20-25% as a safety margin. So at the end of the dat when the truck may be more than capable of handling north of 12k on the rear axle, end users end up with 1.5k for safety.

Not looking to start that argument, just saying…

Its all about not getting sued the way i see it but the only thing i can truly see being different between the 2500 and 3500 is where the springs sit… where the leafs sit is further out to the wheels almost 12” both sides so then leverage comes in to play as to not bend the axle tubes when loaded but i think that would be a far stretch as all we can do is speculate… i know i have far surpassed the 6000 on my rear axle and it has been fine the truck was not even on the bump stops…

 

[ddphillips52]

When I had my SRW 3500, the limiting factor was the tires, not the axle.