2020 Ram 5500 4x4 6.7 diesel front end rattle

[Johnny McGhee]

The truck is a 2021 Dynamax Isata 5 class C motorhome. It weighs just under 20K and now has just over 7000 miles on it. The only suspension modifications are front air ride and front Rancho shocks, both installed by Dynamax.
What started out as a barely noticeable rattle in less than 1000 miles became a unbearably loud banging according to speed and tire pressure. Dodge said they couldn't find anything and no longer under warranty anyway. I realized with the speed of the rattle it was connected to the bounce of the front tires not the sway of the truck, the dip of road, or turning. I can lower the tire pressure from 80lbs to 60lbs and drop the rattle some, but the body roll now is dangerous.
I started with the sway bar grommets/bushings at the links, then the links themselves, then later in this process actually removed the sway bar and links completely and test drove. Rattle still there. I spent hours underneath with a rubber mallet and found some rattle in both front calipers so I removed them and greased the guide pins with no luck. Tightened all 6 body bushing bolts, all shock bolts, all eight of the four link bolts, and anything else I could find to put a wrench on. I found slack in both upper ball joints so I replaced both, slack is now gone rattle is still there. The slack in the upper ball joints was in and out, so i set up a dial indicator to measure vertical play, drivers side had none and passenger side had .006". No grease fitting on the lower joint. Turning the steering wheel hard and fast I found a rattle in both ends of the drag link bar, installed new bar but still rattles.
I'm getting ready for a cross country trip and really can't leave out with this going on.
Hopefully someone has seen this and has a direction to go from here.

 

[gprguy]

I've been thinking about this problem for a few days and I haven't come up with an obvious solution - this is the kind of thing that's pretty hard to diagnose over the Internet.

The only thing that occurred to me is it seems like you had a lot of loose/worn components that you've found and fixed. Is there any chance the front tires wore funny or cupped while the front end was loose? Have you tried to have the front tires road force balanced, or if you want something more DIY, try a set of centramatics on the front? The centramatics might end up masking the actual issue, or they may not be able to overcome the vibration if the tires are bad enough.

I have an extra pair of centramatics but unfortunately they are for the rear axle, not the front.

Probably a long shot to be honest. My only other thought is front shocks - it seems unlikely that the front shocks would be worn out so soon, but who knows. I don't have a great history with Rancho stuff myself. Probably a personal problem...

 

[Johnny McGhee]

gprguy,
thank you for responding. Although I agree that cupping or any type of tire imbalance could cause this, This only happens when the tires go over some kind of bump. The faster the truck is going the smaller the bump that is needed to make this noise. On a extremely smooth road 70mph is smooth as I could ask for, on a very rough road the noise can be unbearable. Using 2WD or 4WD doesn't seem to matter either way.
Both shocks are showing signs of wear, seem a little weak to me and the adjuster valves don't seem to effect it much, there is nothing loose inside and the mounting bolts are very tight.
I have since replaced both lower ball joints which required the purchase of a Larger ball joint press, welding together several receiving tubes, and fabricating an 16 degree adaptor to be able to press the new ball joints in. Yes, Snap-on makes the adaptor but just couldn't see $226.00 for that.
I completely removed the front air ride system yesterday, cleaned and inspected and found nothing wrong with it.
Reinstalled it and test drove with the same results.
I removed the shocks again for inspection and test drove it without shocks at all and if anything it was worse.
I recently read about brake pad issues causing a serious rattle so so I tested hard braking during a rough section of road and it did seem to quiet it down a little, so today I pulled the calipers and installed new pads, clips, all greased properly, and no change. Thinking back on your suggestion on the shocks, they will soon need replacing anyway I might just go ahead and replace the now.
This whole thing is crazy, throwing this much time and money at a truck that is almost new.

 

[gprguy]

No problem, I wish I could be of more help.

Just to be clear, this is a banging and more up and down oscillation when it happens? It's not death wobble, whipping the steering wheel back and forth?

If it's the former and the tires just don't have enough dampening, I am not sure what it could be other than the shocks.

If it's the latter and more of a death wobble type situation any of the joints in the suspension could be suspect. The Ram chassis cab components are all much larger but the basic design is pretty much lifted from the Jeep XJ/ZJ/TJ/etc front end and those are very susceptible to death wobble when you have a worn out bushing somewhere in the system, or a loose track bar.

 

[Johnny McGhee]

Yes the banging is up and down oscillation, no wobble in the steering at all. My 97 Ram did it one time and I replaced everything.
I'm still leaning to shocks but I will take a close look at the tie rod and track bar first today.

BTW, I looked through your build thread. I'll go back later and read through the rest of it. Beautiful truck!!

 

[CdnHO]

Jack it up and hit the tires with a mallet. If it rattles it may be easier to locate the source.

 

[Johnny McGhee]

CdnHO,
I've got a favorite large rubber mallet I use for that. I've about wore it and myself out beating every place I can hit and not cause damage. On the front tires I tried the mallet, then a
3 lb. then my 8 lb. with a medium swing. It appears to only do it with up and down motion or I guess the tire banging on the pavement. I haven't figured out how to duplicate the fast up and down yet.

 

[Johnny McGhee]

When the rattle went from notable to overwhelming I was on a very long section of I-40 this past spring with horrible sections of pot holes. (like three hours) Both front tires were getting a beating. What about the front caliper mounting brackets and guide pins having excessive wear or even damaged due to this beating?? I have inspected ,cleaned, and greased them but I do still get some rattle from them with the rubber mallet.

 

[gprguy]

BTW, I looked through your build thread. I'll go back later and read through the rest of it. Beautiful truck!!

Thanks! It's getting there - slowly..

When the rattle went from notable to overwhelming I was on a very long section of I-40 this past spring with horrible sections of pot holes. (like three hours) Both front tires were getting a beating. What about the front caliper mounting brackets and guide pins having excessive wear or even damaged due to this beating?? I have inspected ,cleaned, and greased them but I do still get some rattle from them with the rubber mallet.

I have never seen something like that happen, but anything is possible I suppose. I know how bad I-40 is in areas..

 

[Johnny McGhee]

I've removed the caliper brackets, cleaned the mounting pins and the pin sockets. Measured the wear on the pins and found .011" on all four pins and assume roughly the same in the pin sockets. I ordered new caliper assemblies and installed the new brackets and pins. And again no change.
I decided that I would need new shocks anyway so I ordered new, after comparing them The original shocks were worn and weak. Installed the new shocks starting at their stiffest setting and had a notable difference, adjusted them down till it was about 20% of the original rattle, however when it did rattle it was just as loud as always. I then brought the tire pressure back up to 85lbs and found it's just as bad as ever.

 

[gprguy]

So when the shocks are stiffer, the rattle is better, when softer it is worse? It sounds like an oscillation or something, but that doesn't make sense with new shocks.

I'm out of ideas at the moment. Have you talked to Kelderman? Their techs are pretty sharp in my experience, maybe they've seen something like this before since it's their kit.