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Old 05-23-2011, 01:04 PM   #1
dpam
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Beefing up the truck suspension

I have a 2008 2500 HD Duramax GMC Sierra 4x4, regular box, crewcab, I have LT 265/70/17 tires (same as one ton) and the GRAWR is the same as the one ton. I would like to safely carry more weight in the truck box while pulling our 5th wheel. I have Firestone Airbags to level out the truck, but I know the airbags don't increase the suspension. I'm thinking of adding an extra leafspring (possibly Timbrens), but I`m wondering how much additional weight can I safely carry by adding the additional springs (leafsprings = how much additional weight?). Anyone have experience with adding additional leafsprings in order to carry more weight.

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Old 05-23-2011, 01:58 PM   #2
NCFischers
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Is the frame the same as a one ton?
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Old 05-23-2011, 02:58 PM   #3
CamillaMichael
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Some of our members have done mods to their TVs and have noted that each factor (tires, axels, suspension, etc) must all be accounted for when attempting to increase towing capacity...leave any one out, and you may have problems. Good luck!
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Old 05-23-2011, 03:23 PM   #4
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GM has 1ton single rear wheel, much the same as your 3/4. Go to dealer and see parts book. I think you will find that 1ton has overload springs that you can add to yours and be equal spring strength. Do not overlook tirewall strength, must also be increased. Also check on sway bar strength. These upgrades will put you in the ballpark.
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Old 05-23-2011, 03:32 PM   #5
kdeiss
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Basic difference 3/4 HD 2500HD and 1 ton 3500HD Additional Leaf Springs,higher weight class tires and wheels
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Old 05-23-2011, 03:51 PM   #6
dpam
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My next door neighbour has the same truck but in a one ton (3500). I'll have to check out the sway bar. The only difference that we can tell is that he has an extra leafspring. We have the same axel and same tires. I'm not trying to turn my 2500 in to a 3500 (one ton). I just want to carry more stuff (weight) in the box of the truck. I guess I'll have to go to a suspension shop and see if they can tell me how much weight an extra leafspring will carry.
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Old 05-23-2011, 04:30 PM   #7
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I believe Chevy is like Dodge...the only difference between the 3/4 and 1 ton is the overload leaf which is above the regular spring pack and only engages (contacts the spring pads) when the suspension is compressed somewhat.
However, if you have the Firestone airbags, I don't think you really need additional leaf springs too. Properly adjusted air pressure in the bags should give you all you will need IMO.
I don't know how much weight you intend to put on your truck, but the limiting factor may well be the tires. I believe my Dodge rear axle rating is around 6,100 pounds with the AAM 11.5 rear end and I am pretty sure your Chevy has the same (or very similar). Make sure your tires are rated accordingly and with about 50-75 lbs. in the airbags you will be able to carry all the weight you would want to safely!
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Old 05-23-2011, 07:11 PM   #8
dpam
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Kingdaddy,

My GAWR is 6084 lbs and my tire rating is 3195 lbs on LT265/70/17 tires. I have Firestone Airbags, but I was lead to believe that the airbags did not act as a leafspring. So am I mistaken and the Airbags do act as a leafspring and support the suspension. I assumed they were to simply level out the truck. I assume if they act as extra support for the suspension I don't need an extra leafspring. Are my assumptions correct?

Thank you for your input.
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Old 05-23-2011, 08:16 PM   #9
kingdaddy
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I wouldn't exactly say the "airbags acts as a leafspring" but yes, they do more than simply "level out the truck".
They increase the spring rate depending on how much air pressure you put in them. The reason they level the truck is that they work to prevent the "sag" that occurs when you put weight on the truck and compress the springs. Your stock leaf springs will compress (or flatten out) as you put weight on them thus allowing the rear of the truck to "squat" or "sag". As you know, this is not desireable for several reasons.
Air bags are a proven technology (many big rigs use air bags) and the adjustability is one of the best parts...when you are unloaded you can let almost all the air out for a stock ride (spring rate) and then increase air pressure when needed to support more weight with proper ride height and a more firm, controlled ride due to higher spring rate.
How much pressure have you put in your air bags? Do you find it is inadequate?
Hope my explanation is helpful...not sure I explained it well.
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Old 05-24-2011, 07:22 AM   #10
dpam
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Kingdaddy,

Thank you for the explanation on air bags. I have been running the airbags at 50 lbs with the monty on the truck. The truck and trailer seem to be the most level at 50 lbs.

Thank you

PS - Thank you to all that sent me their input.

David
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Old 05-24-2011, 11:59 AM   #11
kenandjudy
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Dave I like you have a chevy 2500HD, which I had before buying the Monty 3455. Empty I was within the weight limits but if I loaded up the 5er to it's rated cap. I would be overweight. Along with being over I was concerned about being stopped and ticketed. I found I could retitle the TV and Monty to a gross combination wt. of 24,780lbs. by installing a 1 Ton spring package, but the spring package had to be OEM. This is what is req'd in Pa. Hope this helps.
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Old 05-24-2011, 12:58 PM   #12
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if your adding weight to the front of the box.then alot of the weight is going onto the front axle .if your adding the wieght behind the back axle then alot of the weight will go on the back axle.timkens and air bags do all most the same thing in threoy.i would load the truck with everything you want then weigh the unit .then take the extra stuff out of the box then weigh it again .then you will see were the weight is going. then see what needes to be done .good luck
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Old 05-24-2011, 06:15 PM   #13
ray fischer
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From all of the research I did as well as several other members, the only difference between 3/4 and 1 ton SRW heavy duty Dodge and Chev/GM diesels is one leaf in the spring pack. Adding the leaf gave me 900lbs add'l suspension, although it is not official as far as registration. I added air bags initially, but they only level the load. Air bags do not increase suspension. The axle, brakes, frame, tires are the same 0n 2500 and 3500 SRW. If I knew then what I know now, I would have ordered the 3500 SRW, although I would have also put air bags on to stay level. My 2500 had 3300 miles on it when I bought it and saved enough not to pass up.
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Old 05-25-2011, 05:56 AM   #14
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Lots of guess work in this thread...get a dually...all problems solved!
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Old 05-25-2011, 01:12 PM   #15
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Do a search on this topic and you will find additional information. The only other difference I was able to find between the a 2008 2500 HD and 2008 3500HD SRW besides the overload springs was the OEM part number for the rear axle bearings. I haven't physically compared them to see if they are in fact different. IIRC LT265/75/R16 tires will give you 3415#'s capacity and are nearly identical in diameter to your 17 inch wheels. No need to change your truck's computer tire size setting. The payload for a 3500 is about 700#'s more than a 2500. The change to the higher capacity tire more than accounted for that difference in my truck which came with the stock LT245/75 -R16's. Since the 17's were optional for the 2008 2500 and the stock was 16's you should have no problem finding someone willing to make a swap rims with you. Just another option you may wish to consider.
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Old 05-25-2011, 06:37 PM   #16
kingdaddy
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Quote:
quote:Originally posted by ray fischer

I added air bags initially, but they only level the load. Air bags do not increase suspension.
Ray, I have to respectfully disagree... I'm not sure what you mean by "airbags don't increase the suspension" but the air bags DO increase the spring rate. All you have to do is put about 50-60 lbs in them and go for a drive unloaded!
The reason they level the load is because of the increased spring rate which resists the compression of the leaf springs under load.
Now if you put longer shackles or blocks under the spring pack, THEN you are changing ride height without changing spring rate.
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Old 05-26-2011, 02:32 AM   #17
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I'm not mechanically inclined enough to debate the issue. I just passed along the info that was explained to be that air bags do not increase the weighjt rating or amount of weight that can be carried. They are designed to help carry the weight more effectively, that is level. Only by adding the extra spring will increase the ability bearing capacity. This was explained to me by the spring shop that did the installation, as well as Firestones literature that came with the springs. They were rated to 5000 lbs, but do not increase suspension rating. Dodge uses one extra leaf in the spring pack on the 3500 SRW over the 2500 H/D CTD, not an airbag. Thats the only difference. I went over this with the parts mgr at the Dodge dealer.
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Old 05-26-2011, 04:51 AM   #18
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Ray,
That's the way things were explained to me too. The bags help you keep your tow vehicle level which is a safer way to be. As I understand the weight things there are many other variables besides just a couple of springs. But like you I am not an expert and have pretty much exhausted the extent of my meager knowledge on this subject. I know that we started with a PSD 250 and I either had to get bags or springs or Timbrens or some sort of leveling device or a smaller trailer OR a bigger truck. That was when we traded our 250 for a 450. So far the exchange has been worth the trouble and expense of switching.

Travel safely, Dennis.
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Old 05-27-2011, 06:08 AM   #19
kingdaddy
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It is true the air bags won't change the manufacturer's capacity ratings of your truck because the limitations are very likely going to be something other than your rear springs e.g. your combined weight rating, rear axle rating, tires etc, etc.
Since it is aftermarket, not factory installed, neither the truck nor the air bag manufacturer are comfortable allowing a change to official ratings. Totally understandable, but my point was simply to point out that the bags actually do increase your load carrying capability from a practical standpoint because they increase your spring rate which result in your truck being able to remain level while heavily loaded.
It does seem like everyone is pretty happy with how they work, lots of people seem to like the Timbrens too.
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