Shudder, shake and shimmy.

[Hotdogs]

Hey everyone,
Looking for your insight and experience here. 2020 XLT FX4 super crew with 34k miles. No mods - all stock.
Over past 1k miles noticed two separate issues:
1) truck vibrates at 70-80 mph, both under power and while cruising/coasting. Same experience whether using cruise control or not - smooth roads or janky highways - felt in body of truck, seats vibrate, steering a little. Truck was recently at dealership for this - had alignment and balance done- was not resolved and I was told techs couldn’t replicate, which makes me wonder if they actually drove it.
2) shudder/vibration when braking - but really only when going downhill - I travel a lot through mountain areas, and on paved roads when decelerating from 45/50/55 feel a shimmy/shudder coming from rear of truck. Feel it in brake pedal, not steering wheel- thinking rear rotors. At dealership they shave off a small increment from rotors, but this has had no effect and issue still present.

So- looking for your thoughts. I’ve read through forum posts and see an issue with vibration at 75mph resolved by new tires. The current tires (Dynapro ATM 265/60R18/110T) still have reasonable tread, and have been rotated with each oil change at 5k….
Braking issue- could it be as simple as rear rotors needing replaced? But what would cause/lead to a warping in rotors?
Especially at only 34k miles?

Thanks in advance for all the help.

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[Max Crafter]

I myself would look at your driveshaft carrier bearing while you were at it.

 

[Fawnbuster]

I had to have my tires road force balanced, had a vibration at 70+

 

[Hotdogs]

I myself would look at your driveshaft carrier bearing while you were at it.

Thanks. If a driveshaft carrier bearing were faulty, wouldn’t the truck vibrate at all speeds? I don’t get vibration at 45-60….so maybe just go slow and tick everyone on highways off

 

[Frenchy]

I want to see the alignment sheet. Something tells me the toe is not set right.

As for the braking I suspect you have warped the rotors. When in mountain areas and constantly riding the brakes this tends to happen. I suggest start engine braking or use tow mode and it will engine brake for you.

 

[Hotdogs]

I want to see the alignment sheet. Something tells me the toe is not set right.

As for the braking I suspect you have warped the rotors. When in mountain areas and constantly riding the brakes this tends to happen. I suggest start engine braking or use tow mode and it will engine brake for you.

Thanks. After recent dealership service visit I asked for the alignment numbers. Guy working desk didn’t have em, and gave me runaround about going to get. I was rushing to get out so didn’t press issue. Will be following up.

hear ya re engine braking. Usually my approach anyhow- although admittedly have also been using cruise control setting which I’m curious - does cruise control slow down via applying brakes or downshifting engine? I’m guessing it’s actually using brakes and not engine which could def contribute…

 

[Frenchy]

Thanks. After recent dealership service visit I asked for the alignment numbers. Guy working desk didn’t have em, and gave me runaround about going to get. I was rushing to get out so didn’t press issue. Will be following up.

hear ya re engine braking. Usually my approach anyhow- although admittedly have also been using cruise control setting which I’m curious - does cruise control slow down via applying brakes or downshifting engine? I’m guessing it’s actually using brakes and not engine which could def contribute…

If using tow mode with cruise control it will engine brake. The only manufacturer I have seen apply the brakes automatically with cruise is Subaru and I think it's the dumbest thing ever

 

[Joeiconic]

I had to have my tires road force balanced, had a vibration at 70+

Agree with this. It sure sounds like your rear tires/wheels are out of balance. Make sure you get a road force balance, it can work wonders.

 

[Msfitoy]

When my larger 285 tires were new, they were smooth...at near end of their life and tread wear, they were vibrating past 70 due to rubber wear and imbalance...after installing new tires/balance, smooth again...could be your tires are worn and come out of balance...since they still have good deal of life left, I'd have them rebalanced...

 

[Fawnbuster]

Agree with this. It sure sounds like your rear tires/wheels are out of balance. Make sure you get a road force balance, it can work wonders.

I had one on each axle that needed to be turned on the wheel, one only about 5 degrees and the other was 180 degrees, nothing but smooth riding since.

 

[rang19ca]

I also feel that you have a tire balance issue and Roadforce balance should be done. if you get the vibration while braking then it is a rotor issue.

 

[Joeiconic]

I have another car with 19” low profile tires. Recently had the tires swapped out and upon leaving the tire shop I noticed the rears were out of balance. Took them back and they rebalanced them and they were still out of balance. They said It must be the tires and replaced both rears. Left the shop with the new tires and - out of balance. Decided to go to the dealer (BMW) to see maybe if a wheel was out of round. They road force balanced and told me that all four tires were out of balance and that one rear tire was defective and couldn’t be brought into spec. Went back to the tire shop and they replaced the tire and to their credit they agreed to refund my installation costs. Moral of the story - try another shop!

 

[Rocketeer61]

Strider started doing this at about 29,000 miles. Replaced the factory rubber with BF Goodrich All Terrain T/A KO2s and the vibration disappeared. Also, I seem to remember a car I either had or knew about 40 or so years ago that suddenly started doing the same thing. Turned out a driveshaft balance weight had come off.

 

[Fitzmotor]

If the vibration is worse off throttle downhill, I would make sure the center support bearing is good, and the pinon angle is not too low, it drops on decell, if you give it throttle does the vibration change?

 

[Hotdogs]

If the vibration is worse off throttle downhill, I would make sure the center support bearing is good, and the pinon angle is not too low, it drops on decell, if you give it throttle does the vibration change?

Thanks. So two things here- if on highway and let off gas, when traveling 70-80, vibrations continue until getting down to 65ish. Makes me think balance alignment issue. When going downhill, vibration only occurs when pressing brake, so makes me think rear rotors…steering wheel doesn’t shimmy…

Now, when decelerating on highway from 70 to whatever, the rear end doesn’t vibrate or shake as it does when going downhill….that’s what really makes me confused..almost as if angling nose of truck downhill somehow impacts brakes shaking.

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