Upgrade truck suspension

[Hardscrabble]

Hi all,

Just on the shakedown trip with the new rig, a NL 8-11 and a 2019 Chevy 3500HD Duramax. Over all I am happy with most of the handling, certainly the acceleration and pulling power is fine. We do have StableLoads (upper) installed. I am seeing that I don't like the "hobby horse" bouncing when we hit uneven pavement, expansion joints and the like. It seems in searching the many threads that even though the truck is brand new that the front shocks are most likely the issue, that replacing the front shocks with Rancho 9000s might be my best result. I just want to confirm my thoughts here. The truck sits about level.

Any thoughts?

Regards, Tom

[jimh406]

ardvark wrote:
For my next step, I am going to leave the front shock setting at 6 and I am going to increase the engagement on the rear overloads and try dialing back the rear Ranchos settings. The beauty of the Ranchos is they make it possible to try a lot of different shock rates.

Since you have so many adjustments, why not try changing the fronts as well? I don’t know what tires you have, but you probably could also try different tire pressure. If you don’t want to go down, you could try going up in the front. I think you’d probably have some pressure to work with in the rear. Based on the weights you posted, you probably can drop the pressure on the rear tires.

Fwiw, I use Energy Suspension Bump Stops on my current truck and did as well on my SRW, but I used them to engage the overloads when I had air in the airbags. I find airbag pressure makes the ride more plush generally. You camper is a lot lighter than mine, however.

[ardvark]

jimh425 wrote:
If the shocks made no difference, it sounds more like death wobble not porposing. That would mean your suspension parts could be worn, out of alignment, or stabilizer worn out or all. You can read about death wobble on Ford trucks at the Ford-trucks.com site.

The bandaid is adding a double shock steering stabilizer in addition to your stock one.

Porpoising is an out of balance issue. The front and rear are responding at dramatically different rates which cause the rocking. If you changed your shocks on the rear to 1 for example, you should see a different behavior. That being said, I ran 6 in front and 9 in back with my 9000s when I had a SRW, so those numbers are what I would expect.

If shocks were going to help, you should have already seen the benefit.

I did not say the Ranchos do not help. They do help, they just do not entirely eliminate the problem. The shock settings are so widely known, I think they would be regarded as the standard on TC with Rancho shocks. And changing the shock settings does dramatically impact feel.

The harmonic sets up on certain sections of highway with expansion joints. As I noted earlier, it is maddening when it happens but fortunately is very seldom.

As noted earlier, the variables involved in handling and suspension are great in number so what works for one often does not translate directly to another combo which I think is why the discussion has gone on so long in so many different forums.

If it were not such a pain, I would like to change out the front springs as I think the stiffness of the plow springs plays a part. Before installing the Ranchos the front was so stiff it was hard to tell the truck had front springs.

For my next step, I am going to leave the front shock setting at 6 and I am going to increase the engagement on the rear overloads and try dialing back the rear Ranchos settings. The beauty of the Ranchos is they make it possible to try a lot of different shock rates.

Thanks for the thoughts. 🙂

Steve

[jimh406]

If the shocks made no difference, it sounds more like death wobble not porposing. That would mean your suspension parts could be worn, out of alignment, or stabilizer worn out or all. You can read about death wobble on Ford trucks at the Ford-trucks.com site.

The bandaid is adding a double shock steering stabilizer in addition to your stock one.

Porpoising is an out of balance issue. The front and rear are responding at dramatically different rates which cause the rocking. If you changed your shocks on the rear to 1 for example, you should see a different behavior. That being said, I ran 6 in front and 9 in back with my 9000s when I had a SRW, so those numbers are what I would expect.

If shocks were going to help, you should have already seen the benefit.

[ardvark]

jimh425 wrote:
What are shocks set to loaded?

Nine on the rear, 6 on the front. However, problem was the same with stock shocks.

[jimh406]

What are shocks set to loaded?

[ticki2]

Sorry Ardvark had your rig mixed up with th OP

[ticki2]

My scale weights are unloaded 4320# F and 3960# R . Loaded its 4400# F and 7220# R . Keep in mind truck is an older drw with different camper . I'm surprised your' s is adding 300# to the front , that might be a contributor . WHat is your front axle rating . Can you narrow it down to what roads cause the problem . I know the truck is new but I had a similar problem in a new 73 Dodge van . It turned out to be an internal nut in the steering box that backed off . If you can duplicate the problem it may be time for a dealer visit .

[ardvark]

Sticker info on 2012 F350 SRW LB Gasser
6,000 front plow axle 7,000 pound rear 11,000 GVWR Payload not to exceed 3,829

Truck - me, wife, and a full tank of fuel Front 4,440# Rear 3,200#
Truck as above with Hallmark UTE wet Front 4,740# Rear 6,080#
Truck as above with Northstar Laredo wet Front 4,820# Rear 6,120#

Steve

[ardvark]

ticki2 wrote:
What are the front and rear axle weights from the CAT scale and was the camper wet and loaded for camping at the time ? What are the Rancho shocks set at front and rear ?

I have both for the truck and with both truck campers, Hallmark Ute and NorthStar Laredo. As you know these are both light weight TCs and the problem was the same with each. Weights are fully wet and ready to travel. What weights would you like and if I might, what are yours?

[ticki2]

What are the front and rear axle weights from the CAT scale and was the camper wet and loaded for camping at the time ? What are the Rancho shocks set at front and rear ?

[ardvark]

jimh425 wrote:

ardvark wrote:
Do you have a suggestion of what you think will work?

I have questions, first.

What mods do you have on now?

What tire pressure are you running?

I have Rancho 9100s all the way around and the Hellwig sway bar. That's it. Tire pressure is per door sticker: 65 front and 80 rear. I also have my CAT scale weights and an within my GVW, again per door sticker.

[jimh406]

ardvark wrote:
Do you have a suggestion of what you think will work?

I have questions, first.

What mods do you have on now?

What tire pressure are you running?

[ardvark]

jimh425 wrote:
Seems like OP has left the building.

I don’t believe porpoising is insurmountable unless you continue to use the same approaches that didn’t work. There just aren’t that many parts.

While it is true there are not that many parts, if the harmonic that sets up is not caused by or controlled by the parts that are realistically swapable, it is a tough go.

I have researched threads on this topic that go back at least a decade and noted some folks who replaced part after part with at best limited success. I need to make a video what we have the camper on the back and the porpoising starts. It is not just a motion. The truck literally sounds like it is going to tear itself apart and dropping down to about 40 mph is the only thing that seems to work. This is after a the second set of shocks, Super springs, and a Hellwig sway bar.

I purchased Torklift uppers, but after receiving them and noting if I installed them my overloads would be engaged even when empty, I called Torklift to discuss the situation and ended up returning them. I now have fabbed my own uppers, but with the weather have yet to try them out.

I wish there was a simple solution, but I think it is more elusive than it may appear to be. However, the problem is not constant or even frequent, the vast majority of the time, it is a nonissue on our combo.

Do you have a suggestion of what you think will work? 🙂

Steve

[PhilR]

Forgot to mention in my previous post....althought my combo is identical to the OP's rig, I have the plow package on my truck which includes a higher rated front axle.