Shaky Springs!

[Hozr]

Shaky, vibraty, wiggly....whatever.

Since the engine swap my front coils vibrate like they are trying to get air out of concrete. In fact, they vibrate so loudly you can hear them over the engine!

Coils are WH 4.5 Rockcrawlers. Engine is a 4BT. Winch bumper, etc etc. I'm concerned they might be too soft up top with the additional weight up front. Bronco drives nice but is a little squishy. Hellwig sway bar is on order.

Trying to decide if I should find linear rate coils or if anyone makes a vibration damper of some sort to shut these stupid things up!

 

[Justafordguy]

I know those 4Bts are rough but that's just crazy.

 

[Hozr]

I know those 4Bts are rough but that's just crazy.

It's actually not crazy in the cab, it just seems to be a frequency the springs REALLY hate. I'm toying with Idle setting as well but it's still pretty funny. I'll try to get a video.

 

[Skiddy]

What shocks are you running

 

[Hozr]

Rancho 9000's

It will do it standing still as well. It's a funny side to side motion in the spring that I think comes from the progressive rates. <- totally guessing.

 

[Apogee]

The 4BT is probably just perfectly hitting one of the natural frequencies of the springs. A different spring with a different rate would probably change the frequency enough to not have the same issue. That said, you could increase the rate of the spring with something like this or possibly add top or bottom pads to isolate the spring and damp out whatever is driving the vibration. When dealing with harmonics, changing the mass of the system is usually the first thing to look at, but just looking at a spring as the system makes that less of an option I would think.

I can't imagine it is having any negative impact on the performance of your suspension, but I can see the noise being an issue since they must be hitting the coil towers.

Can't say I've ever heard of this problem before.

 

[DirtDonk]

Next time you roll up next to a Harley/Davidson chopper at a street light, check out the front tire while it's idling and you'll see Apogee's harmonic dynamics in action.;D

Paul

 

[sprdv1]

next time you roll up next to a harley/davidson chopper at a street light, check out the front tire while it's idling and you'll see apogee's harmonic dynamics in action.;d

lol.....

 

[Hozr]

I figured it was a harmonic issue as it happens a a couple of RPM ranges but not all. The performance and drivability are good which is why I don't really want to swap the springs.

Not sure how the coil spacer will affect the front end. Another friend suggested cutting a piece/pieces of hose to fit around the coil in a few places.

 

[Rustytruck]

We use to run air lift air bags inside the coils. they use to make a kit like this for the early Bronco back in the day. it fits inside the front coils.

https://shop.broncograveyard.com/Fr...MIttHuq6WV3QIVz19-Ch3KPQ10EAQYAyABEgIa__D_BwE

 

[DirtDonk]

I think the hose would be more work than it's worth frankly. I doubt the little spacer things are going to change things enough to feel with all that engine weight working against them.
But I don't know that for a fact either. They are designed to shore up a sagging spring after all. But seems like they would reduce harmonic influences too.

Then there's the old air bag option too. Should dampen harmonics as well, to maybe even a higher degree than the little thingies would. Can (and will) also effect ride of course, depending on how much air you keep in the bags. Not sure if it would be annoyingly more or not.

Everything has some kind of effect.

Paul

 

[DirtDonk]

There 'ya go! Beat me to it.

Paul

 

[Apogee]

Rather than a hose, I was wondering if you could use something like a heavy gauge heat shrink...slip it over and shrink it down. I don't know if it would make any difference, but it probably something I would try. Alternatively, you could fabricate new spring towers such that they couldn't hit given the amplitude of the vibrations you're seeing. It doesn't stop the harmonic, but it should stop the noise resulting from it.

 

[Rustytruck]

are your engine and tranny mounts rubber isolated?

 

[Hozr]

So, it's the progressive coils. The tops are so bound up the slightest weight to the truck makes the coils chatter against each other.

I took a video and just pulling down on the fender with my hand makes it come and go.

 

[Hozr]

are your engine and tranny mounts rubber isolated?

Yea, Marine mounts