I'm planning on purchasing a new truck in the next couple of months and have been interested in the F150, but I've been hearing about the vibration issue.

Here's my concern, coming from an engineering perspective. Ford advertises the new F150 as having the "strongest frame in its class", and references its "fully boxed frame and stiffer body structure." It is well known that closing in a C-frame will definitely increase strength, so why is Ford to be the first to do this? Well, if you look at a frame on a heavy rig you won't find a closed in box frame. The reason being is that if you were to close in the C-frame, the strength of the frame would increase. That's bad because the frame strength will decrease frame torsion, which absorbs road and engine vibration.

A C-frame is, believe it or not, part of the suspension of the vehicle and is needed to absorb engine torque, engine/tire vibration, and road irregularities.

If Ford is serious about determining the cause of this issue then they should cut an inch-and-a-half wide piece of the inside of the frame out on one of the trucks and see what happens to the vibration. Stronger isn't always neccessarily better.

Sorry if this has already been posted, but I've been skimming through the past posts and didn't see anything related to this.

 

If this were true, wouldn't all F150's have the vibration?

 

Youn know....that makes more sence than any of the other attempts to fix this problem.

I would really like to see that also.

 

I second that.... it's a small percentage that have the issue. If the frame was messed up, I'd think we'd ALL know about it. A fully boxed frame is nothing new to the automotive world.

EDIT: Oh yeah, from and engineering perspecitve your comparing apples and oranges! A big rig frame compared with a light-duty pickup?! Two COMPLETELY different approaches.

 

as another fellow engineer in automotive for 10 yrs I agree on the frame as the root cause. I was at one of the ford WOW tours where they demoed and explained the vehicle. one demo consisted of the 4 competitive truck frames. they were pinned at the front rails and supported on one rear end. a lever allowed you to put torsion on the unsprung frame end and showed the difflection in x.xxx inches. toyota = 14" with my weight, a noodle. the gm about 5", the dodge (fully boxed and surely ford's benchmark) about 2". and the ford was 1.7"...(best in class) they explained this torsional stiffness was 9 times greater than last year's model. they also explained how this is beneficial. the stiffness allows very stable handling in a quick avoidance maneuver as the truck acts as a whole. the toyota they felt was down right dangerous with the excess box sway in a maneuver. i witness this handleing on the ride and drive. the ford was tops.

but as mentioned this comes at a price. the suspension can now be longer traveling and better tuned but at the same time NEEDS to be longer traveling for a similar ride.

bottom line, the natural frequency of this super stiff frame falls in with typical small road inputs that were normally absorbed by flexier frames. this truck is great in significant pot holes and the like, but hates small bumps and skips in the road.

the suspended mass damper moves this frequency lower and thus is intended to reduce the harshness from the small road inputs

i am planning to instrument my truck with accellerometers to demonstrate the natural frequency ( i will predict 20 hz) and then compare after installing the mass damper that should reduce some of the oscillation. a fun goverment job for the lab tomorrow

ramb

 

I do agree with both the engineers, I was thinkin about it while on a drive this weekend, no I dont have an 04...however I do put alot of consideration even when not on the boards about peoples problems. I had also come to the conclusion that the frame was not absorbing as much road shock as the old ones did. This is just simply the consequence og a stiffer frame. I am sure there is some type of setup you could do by cutting a section out of the cross frame and installing something, tryin to work up an idea, that will allow the frame to absord the small shocks and flex a little, but will tighten it up when it needs it.

Perhaps one of the engineers here can come up with something

 

my buddies avalanche is really smooth (borderline grandpa's truck) but his acts like a tahoe becaue the box and cab are one. in fact that sail panel has a frame angle member (like a roll cage) needed to prevent body stress from flex as it is all attached

so...what if we fixed the box to the cab somehow, with rigid mounts??? or rubber bushings?? anyone want to experiment with thier $35k truck??

Ramb

 

I'm going to pretend I didn't read that. This truck LOVES the little bumps and skips... it just makes 'em disappear!

This frame rocks, there is nothing wrong with it... you guys are crackin' me up!

 

don't get me wrong. it is an awesome truck. i just clearly notice the difference when compared to my 2001 supercrew, my 1996 GMC, and my 1995 GMC.

maybe it is a particular cab config. i have super crew with fx4 suspension
Ramb

i will settle this with data. then there is no more speculation. that is what us enginerds are trained to do

 

For your info the vibration was noticed the most on mine at 25hrz @ 1500 rpm

 

Hi tthunder

you mentioned 25 Hz at 1500rpm. makes me think you are refering to the driveline vibration that is also mentioned frequently. I do not have this issue. I am refering to the Harshess of the truck as a whole due to road input.

I think there are two separate issues.
just my observation

the only other issue i have is steering "nibble" when applyin gthe brakes. not in the pedal as warped rotors would cause. bu t in the steering wheel and very suble. some say it is the new rack and pinion steering box.

Ramb

 

I have said the same thing since last Nov. These trucks are just not riding like other trucks. All 04' 4x4's I have driven have this feeling. I think they all have it and alot of people don't recognize it. Mine doesn't have a "vibration", but it has that "feeling every bump feeling" that other trucks/vehicles don't have. I think its the suspension/frame setup.

 

I think that's a good thing! There aren't supposed to feel like other trucks! It's the feeling of a refined, solid vehicle. I've owned plenty of ford trucks - this IS the best.

 

They're not suppose to feel the way they feel either! Maybe 4x2's feel different.

 

How are they supposed to feel?! Not rock-solid, smooth and quiet?