Roadmaster Active suspension in a long bed

[NB64]

My 22 F150 has had a slight vibration in the 71-74 mph range since new. It has 7k miles. I recently added a RAS to the truck. It is the 6.5 bed with I’m guessing the two piece drive shaft. It’s been at the dealer for a month. They initially balanced the tires which they reported were all out of balance. They did not test drive the truck even though they said they did. I ended bringing it back because the vibration was worse. Now they’ve done a bunch of tests and just asked if the problem began after I added the RAS.
So my question is, has anyone with a longer bed with a RAS experience a vibration? It’s definitely not a shutter that my 2004 ram 2500 Long bed had. I just added a spacer and fixed that issue. So I do know the difference between the two. The RAS added about an inch of height.
thank you!

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[Snakebitten]

I have RAS on a 6.5 bed and do not suffer any noticeable vibration.

But honestly, if it would help the dealership successfully address whatever is wrong with the truck, I'd remove the RAS for them. Only takes a couple of wrenches and wallah! RAS free truck.

 

[Pedaldude]

What ‘tests’ did they do and did it do anything more than sit at the dealership for a month while collecting dust and getting a wheel balance?

A slight vibration is not a quantifiable measurement and could be anything from imperceptible to the wheel about to fall off depending on the driver.

You might think that the vibration is worse since you hadn’t driven the truck for a month.

A quick peek under the truck will say whether it has the one or two piece driveshaft but generally a driveline vibration will be at a particular RPM, while a tire and wheel issue will be at a specific speed.

Your dealership is shooting in the dark now if they’re asking you if a minor suspension mod is the cause of the vibration. Try another dealership and insist on a test ride with one of the technicians. Some garages have instrumentation for NVH issues and it can quickly get to the bottom of an annoying problem like this one.

It could be a tire issue and the balance machine won’t really solve it if a tire is out of round or has excessive runout. Swapping the wheels around won’t really help, since it’s hard to tell sometimes where a vibration is coming from by just the seat of your pants and it’s possible that two tires are off. Recently, a member weighed his tires and they were off by quite a bit more than you would expect.

It could also be the earliest stages of a bearing going bad or a bad alignment.

Shop around for a new dealer that won’t just park your truck on their lot while they walk past it with their thumbs up their asses!

 

[NB64]

They’ve acknowledged that there is a vibration. Two techs have taken my truck home to further diagnose the issue. To this point they supposedly swapped wheels/tires with another truck. They ruled out the driveshaft ( no explanation) and think they’ve isolated it to the rear end. But most was done after I sent an email to the Assistant General Manager this past Saturday. I’ve been tracking and documenting the dealers activity though the Ford app. They haven’t spent a lot of time with it. It feels like every other out of balance tire I’ve ever experienced. But what do I know.
I haven’t had my truck and they just brought up the RAS on Monday.

 

[DT444T]

wallah!

(voila)

But yeah. If you do something to your truck and a new problem starts, maybe try undoing the thing.

 

[UGADawg96]

I also have RAS on a 6.5 bed and do not suffer any noticeable vibration.

 

[NB64]

I had the RAS for more than 10 years in my Ram 2500. Granted it was a straight driveshaft, but never a vibration from that. That truck made me very knowledgeable about vibrations. The dealer put over a 150 miles on my truck so far.

 

[Polo08816]

I don't think it's going to be the RAS but it is a convenient thing for them to point the fingers at since it's not an OEM product.

Curious - what is the rationale with going with the RAS instead of just retrofitting the Heavy Duty Payload Package rear leaf springs if the goal was to increase the effective spring rate?

 

[Snakebitten]

RAS is progressively adjustable.
It's like the difference between a static damper/shock VS one with adjustable damping.

Not everyone wants the fuss, of course, but it's nice to be able to adjust to loads and conditions.

 

[NB64]

I have a lot of experience with the RAS with my previous truck. It really makes a difference driving empty and loaded. This truck feels more settled especially over rough roads. I plan on a much lighter Rv and should be well below my truck’s capabilities.

 

[NB64]

The Service manager finally called me. The have a Ford Field tech coming to check my truck. The dealer said the vibration sensor pinpointed the vibration to rear end. They did not mention to Ford that I have a RAS system on. So I volunteered to come Sunday switch vehicles and remove the RAS for diagnostic purposes. I thought that was pretty considerate especially that Ford probably just say that was the issue. So on the drive back to the dealer I’ll know as well.
thank you for your help.

 

[NB64]

Tomorrow will be five weeks the dealer has had my truck. I picked the truck up on Saturday and brought it home to remove my RAS and sway bar. Drove the truck back to the dealer, there was still a vibration. The Ford tech drove my truck home last night. I imagine that they used the vibration sensors hooked up to confirm that the vibration was still there.

 

[NB64]

The driveshaft came in today. It’s getting installed tomorrow so, I have my fingers crossed.

 

[HammaMan]

I thought I saw something mentioned about an issue with the compound drive shafts. I could be imagining it. Another variable at play is your front driveline that's now fully engaged starting with the 22s and up 4a transfer cases. All components within the entire driveline could be a potential cause, not just the rear's. I'd be quite surprised if they didn't have a sensor for monitoring vibrational frequencies. That'd tell them a lot. By knowing the frequency it's easier to narrow down when at a set speed as it'd correlate directly to the component by either being a direct frequency of its rotation, or presenting as an oscillating harmonic. (the RAS could in-fact be exacerbating this, but something is present nonetheless)

edited to add GPT's response / explanation for those interested...

The powerboost's trans mount is unique in that it's got a mass dampener on it. Your truck doesn't appear to be one so it's probably not a factor.

 

[NB64]

They used sensors over a period of time and determined that it was the driveshaft. So I’ll know for sure tomorrow afternoon.

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