Ride difference 2500 vs 3500

[rncordy]

A year ago I "upgraded" from a 2500 (coil springs) to a 3500 (leaf springs), both short boxes, similarly equipped. I have the sense that when pulling my travel trailer the ride is much rougher with the 3500, especially so on some of our washboarded Interstate Highways. Can any of you confirm that this could in fact be the case? Thanks

 

[AH64ID]

The leaf springs are a firmer and stiffer ride, which is why they are found on the 3500.

Have you weighed your axles loaded and adjusted your tire pressure for that weight?

 

[Grumpy8811]

you want to smooth out the ride in a 3500 you really have to put a heavy load in it.
2500 is more mushy.

 

[wyosteve]

Your sense is correct. Noticeable difference from my 3500 to current 2500. As mentioned, the leaf springs are more harsh.

 

[AH64ID]

This is one of the reasons I wouldn’t want a 3500 without the auto-level. That being said concrete expansion joints on the interstate are more a wheelbase thing than a suspension thing.

 

[rncordy]

Thanks for the very helpful replies! I have lowered the tire pressures and perhaps could go lower. When towing my 6000lbs trailer I run my tires at 64 front, 74 back. Again, many thanks!

 

[AH64ID]

Thanks for the very helpful replies! I have lowered the tire pressures and perhaps could go lower. When towing my 6000lbs trailer I run my tires at 64 front, 74 back. Again, many thanks!

That’s a lot of air for a 6K TT. You’re probably not at 6,900lbs on the rear axle with that trailer.

Depending on what else you have in the bed you could probably go as low as 50-55 rear.

 

[Cummins12V98]

Different animal but I run 30psi rears BobTail on my DRW with Factory rear air ride. I always run 80 fronts and even with 6k pin weight I am only adding less than 200# to the steering axle. As mentioned use the load/inflation tables for your tires!!! I add 10 psi to the fronts and 5 psi to the rears over the chart. I made it 68k on last set of tires on the DRW towing HEAVY 50% of the miles, it's all about PROPER air pressure.

 

[rncordy]

More helpful thoughts! I do check tire wear and at 22,000 miles it is uniform across the treads.

 

[johnmyster]

On the 3500s, there's an overload spring in the pack. It's on the bottom. It's really thick. Once engaged the spring pack is substantially higher spring rate. It's a "two stage" pack.

I installed Carli mini-packs. It's now more progressive throughout the range than on-off. The packs compress more under the weight of our TT (about 1650 pounds on the ball) but not so much to be nose-high, even with the slightly taller springs up front. You can keep all the factory shims or remove depending on desired ride height.

Your trailer is light enough you could probably consider Thuren full leaf packs if you really wanted to really seek improvement.

I've done some work to pursue ride improvements. Currently: Thuren sway bar and TF-351 (1") coils, Carli add-a-packs, Bilstein 5100...

 

[rncordy]

Thanks Johnmyster, I never thought of that approach, in fact I've never heard of Carli or Thuren. Not sure I want to go to this far ($$ and warantee). The ride is irritating but doable.

 

[johnmyster]

Thanks Johnmyster, I never thought of that approach, in fact I've never heard of Carli or Thuren. Not sure I want to go to this far ($$ and warantee). The ride is irritating but doable.

Some will suggest Sulastic shackles. More sidewall and lower pressure never hurts. On stock size tires, I'd be running 65 F and 55-60 R with that size camper, depending on how much weight you have in the truck/bed.

The Carli and Thuren systems are well regarded for improving ride quality. Lower rate springs and added travel, rather than typical big lift kits that make radical changes to suspension/steering geometry. I kept 5100 shocks rather than go with something stronger, because controlling see-saw motion of a long/heavy TT was a chief concern.

The Carli mini packs are ~$500. (You could probably forgo the more expensive version with the lift block.) I found my set on ebay for under $300. CJC customs might have some good advice for you. Their open-box deals section (and ddp performance) might help with the $$ if you have a plan in place.

Changing front springs was night and day. (Lower spring rate and 1" more travel before contacting the bump stops.) Changing the front sway bar was also very noticeable. Not sure any of it would impact warranty. Folks modify suspension on newer trucks frequently.

 

[lpennock]

On the 3500s, there's an overload spring in the pack. It's on the bottom. It's really thick. Once engaged the spring pack is substantially higher spring rate. It's a "two stage" pack.

Actually it is a misconception that the thick spring is an overload spring. It is actually what gives the spring pack a progress spring rate rather than just a linear spring rate. As the other springs are compressed against that plate it effectively shortens the springs. As a leaf spring is shortened the spring rate increases.

 

[johnmyster]

Actually it is a misconception that the thick spring is an overload spring. It is actually what gives the spring pack a progress spring rate rather than just a linear spring rate. As the other springs are compressed against that plate it effectively shortens the springs. As a leaf spring is shortened the spring rate increases.

Does the term overload have some meaning I'm unaware of?

The spring is not engaged when the truck is unloaded. Engages as the spring compresses: load or bumps. Not only does it shorten the active region of the main leafs, it now becomes an additional spring (leaf) that is added to the pack. Removing it and adding the mini packs (always engaged) makes the springs more linear with likely a higher initial rate (the range when the factory lower overload was not engaged.)

I'm not sure a leaf spring with multiple leafs can be truly linear.

Is there something else we'd rather call it? Lower "additional load" spring?

 

[lpennock]

Calling that thick leaf an overload is what most people call it; however, unlike the rest of the springs in the pack it really doesn't deflect. It just provides a perch for the rest of the springs to deflect into. As the rest of the springs lay against it the spring is effectively shortened and the spring rate rapidly increases.

 

[johnmyster]

Calling that thick leaf an overload is what most people call it; however, unlike the rest of the springs in the pack it really doesn't deflect. It just provides a perch for the rest of the springs to deflect into. As the rest of the springs lay against it the spring is effectively shortened and the spring rate rapidly increases.

Sounds like there's no other name for it. It's another leaf.

IIRC mine was 3/4" thick and the other leafs were 3/8", so it's 8x as stiff. (Stiffness is cube of thickness.) So it's the equivalent of adding eight additional 3/8" leafs of equivalent length to the pack at the point of contact, in addition to the stiffening effect on the other leafs. Still a leaf (it moves with additional load) albeit a really stiff one.

 

[Diesel85]

Sorry, I know I'm of no help, but I felt like commenting. I like the stiffness of the 3500, it feels like a truck and it makes it feel solid.

 

[Grumpy8811]

Sorry, I know I'm of no help, but I felt like commenting. I like the stiffness of the 3500, it feels like a truck and it makes it feel solid.

me too... I have a DRW 3500 because I carry heavy stuff. Lets face it, 2500 and even 3500 SRW's are a bit light in the loafers for when you need to do some real work.. but they do ride smoother and often have more favorable gearing for better unloaded fuel economy.. there is always a tradeoff somewhere, no matter what

 

[Turbo Terry]

My 1999 2500 srw with Firestone airbags rode about as rough as my 2022 3500 srw empty. Not much difference really. But the 3500 sure carry’s the 3000 lbs truck camper more better.

 

[Grumpy8811]

My 1999 2500 srw with Firestone airbags rode about as rough as my 2022 3500 srw empty. Not much difference really. But the 3500 sure carry’s the 3000 lbs truck camper more better.

I think you get about 1000 lbs more payload in a 3500 SRW over a 2500..