Ainít what it used to be... - Chevy and GMC Duramax Diesel Forum
11-16 LML Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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  • 2 Post By jdwarren
  • 1 Post By eli_harper13
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post #1 of 8 (permalink) Old 09-21-2019, 06:33 PM Thread Starter
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Ainít what it used to be...

I have a 12í in great shape. Blackstone says my oil looks amazing at 10k mile intervals. I deleted over a year ago. Got nearly 200k on her and it runs like a sewing machine. Currently running a 30hp tow tune.

However, I feel like itís missing some oomph when I pull even a tandem axle enclosed trailer around 5k lbs. CTS shows normal vane travel and pressures are great and holding. But I just feel trailers manhandle the truck a bit. Even an empty 20í flat BigTex trailer.

Could it be a suspension thing? I just feel like the truck should be taking advantage of the trailer and not the other way around. Does this make sense?



EFILive by RidgeRunner. 🤘 Fuel system support hardware, CCM front Diff Drop, some LEDs to make night into day, got some big ol 20's and wide ass tires and a nice display to show me what's up under the hood-

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post #2 of 8 (permalink) Old 09-22-2019, 01:27 AM
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Originally Posted by Sierraluva View Post
I have a 12í in great shape. Blackstone says my oil looks amazing at 10k mile intervals. I deleted over a year ago. Got nearly 200k on her and it runs like a sewing machine. Currently running a 30hp tow tune.

However, I feel like itís missing some oomph when I pull even a tandem axle enclosed trailer around 5k lbs. CTS shows normal vane travel and pressures are great and holding. But I just feel trailers manhandle the truck a bit. Even an empty 20í flat BigTex trailer.

Could it be a suspension thing? I just feel like the truck should be taking advantage of the trailer and not the other way around. Does this make sense?
Is it a lack of power or a problem with handling? If the latter, are you running your tires at maximum pressure (at least the rear truck tires and all trailer tires)? I find running maximum pressure improves handling, and it also makes blowouts less likely.

As for suspension, it's possible that if the rear shocks are shot it would make the rear end act like a springboard. As load on the rear axle increases the natural frequency of oscillation will get lower and the amplitude will get bigger, which will make it feel like you're boating on rough water if the surface of the road has rises/dips that match that frequency at the speed you're traveling.
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2017 Silverado 3500 LTZ (Summit White) | CC SB SRW | Z71 | Duramax L5P | Undercover Ultra Flex bed cover | Draw-Tite front receiver | AIMS 3kw inverter-charger | Titan Travel Trekker 50-gallon auxiliary fuel tank
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post #3 of 8 (permalink) Old 09-22-2019, 11:48 AM
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I had a 2011 GMC 2500 company truck that the rear springs got weak on after a few years of hauling rig stuff and pulling heavy loads. Pulling a bobcat or mini-excavator got to the point of being almost scary. You may not need to go this extreme but we made my truck a 3500. Spring pack for a 1-ton is a direct bolt in and the holes are already there for the overload stops to bolt onto the frame. Handling and ride was better than I remember it when the truck was new. Look at your rear spring packs, mine went completely flat before we upgraded to the 1 ton parts.

16í C.C. LT. Tinted, Weather Techs, Boost Tow mirrors, leveled on 35ish, Ridge Runner
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post #4 of 8 (permalink) Old 09-22-2019, 02:18 PM Thread Starter
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Iím ready for airbags for sure. With my 1700lb pin weight 5th wheel the bed squats 3Ē. I think the springs are a bit tired.



EFILive by RidgeRunner. 🤘 Fuel system support hardware, CCM front Diff Drop, some LEDs to make night into day, got some big ol 20's and wide ass tires and a nice display to show me what's up under the hood-

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post #5 of 8 (permalink) Old 09-23-2019, 12:27 PM
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Where does one order said 3500 springs?
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2011 LML Silverado 2500HD CCSB Z71, Leveled, Bagged, AFE DFS780 Lift Pump, B&W Companion.
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post #6 of 8 (permalink) Old 09-23-2019, 12:47 PM
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a word of caution - "bone stock" my 3500 "dualie" rode way too rough for us. Let me explain..while this vehicle is primarily for towing either of our two trailers, there are times when we have to use it as a "back-up" second car.

I should also explain that we have pretty rough roads in our area, before you get out to public roads.

Anyway, we just couldn't stand it - so I removed one leaf from the rear "pack". This softened the un-loaded ride enough to be acceptable. Our trailers are 'bumper pulls" - about a 1,500 lb. tognue load. And our 600 lb. jet ski rides in the bed.

Even with that load, she does just fine...yes...the springs now touch the over-load angles. Just to be on the safe side...I have air shocks...run them at 50 lbs. when carrying loads.

That seems to be the answer. Just bear the above in mind if you are going to add springs.
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2013 3500 long bed crew cab. Purchased at approx. 70,000; now have 81,000, convert to CP3. Otherwise bone stock except for air-shocks in rear, together with one leaf removed from spring pack for softer ride. Well....went over a bumpy road the other day & the bone fell off....
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post #7 of 8 (permalink) Old 09-24-2019, 03:04 AM
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Where does one order said 3500 springs?
The springs for my truck came from the dealer, along with the bracket thingys that bolt onto the frame for the overloads to rest on. Don’t remember what it cost, didn’t really care cause somebody else was payin for it

Air bags or just a fresh set of 2500 springs may be the best answer for the OP. The truck I had was carrying a 100 gallon diesel tank, an in-house fabricated headache rack/bed rails/rear rack made out of 2” angle and square tubing, a toolbox full of heavy stuff, chains, sledge hammers, well heads, frac valves, rig parts and whatever else I could throw in it. On top of that it spent a lot of time bouncing around off-road so the more I think about it the more I think they should have just bought me a 1-ton to begin with haha.

16í C.C. LT. Tinted, Weather Techs, Boost Tow mirrors, leveled on 35ish, Ridge Runner

Last edited by Ineedabiggertrailer16; 09-24-2019 at 03:14 AM.
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post #8 of 8 (permalink) Old Yesterday, 09:52 PM
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My rear spring pack is getting tired. I was into the overloads running empty. I installed some airlift bags and have been pleased with the results. Less squat, seems to bounce less (chucking). Cornering is much better while towing. When unloaded I run 5psi in the bags as per the manual. This keeps me out of the overloads. That along with 60psi in the rear tires makes the ride quality very comfortable. I only tow about 12k on a bumper pull toyhauler so in the big picture not much weight though.

06 2500HD CCSB 4wd LBZ | Fleece Trans cooler lines |Red Head steering box|Edge Evolution CTS2 w/ EGT probe| Bilstein 5100s|Bilstein steering damper|Michelin Defender LTX M/S LRE| "OEM" Turbo Brake | Airlift # 88275 airbags
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