Vibration when coasting/deceleration only

[metroplex]

I have a 2017 Fusion Sport that has some vibration/shaking only when coasting or decelerating, most severe at lower speeds like 40-50 mph. As soon as I get on the throttle, the vibration subsides. although if I turn off the radio and HVAC and listen very closely, I can somewhat hear a vibration at 70+ mph but it isn't that detectable through the cabin. The vibration is not felt through the pedals or steering wheel, but rather mainly felt through the seat/floorboard/vehicle itself.

It's AWD, so the driveshaft is constantly spinning when the vehicle is in motion, and there are no U-joints on the driveshaft but rather CV-type joints. I couldn't see any signs of lost weights on the driveshaft.

I suspect the wheels/tires may be at fault here, but I doing a number of searches and asking around has only yielded generic responses regarding tires being out of balance. I don't understand why the vibration is only felt during coasting/deceleration.

 

[spavel6]

Stupid suggestion, but often when I feel vibration on deceleration, I have a few loose lug nuts. Have you made sure they're good-n-tite?

 

[metroplex]

Yes, I actually just rotated the tires about a week ago (the vibration has started about a year ago, so my tires are now rotated to back where they were a year ago) and torqued the lugnuts to OE spec (150 ft-lb).

 

[The Critic]

Originally Posted by metroplex
torqued the lugnuts to OE spec (150 ft-lb).

150 ft-lbs? That seems really high for a passenger car.

 

[DriveHard]

vibrations effected by application or removal of throttle from my experience have always been CV joint issues...

 

[Eddie]

Agree with CV joints as possible cause. I have never heard of a passenger vehicle requiring 150 Foot Pounds of lug torque. Ed

 

[Gebo]

75-80 lbs is more normal lug torque, at least for my cars.

I would start with making sure your lug nuts are torqued to the proper spec, air pressure is correct and then rebalance all my tires.

 

[t1snwrbrdr12]

On decel only seems drivetrain related. Cv joints or whatever style joint the driveshaft uses. Potentially engine or trans mount issues but hard to tell without experiencing it. Have you searched for TSB's?

Wheel balance would be all the time. Lugs being overtorqued doesn't matter to a vibration as long as they are evenly torqued and you didn't snap any wheel studs.

We used to advise against many awd models we worked on at my dealership (just to family and friends) due to vibrations we just couldn't solve. Was especially true with Hyundai's of that era (2005-2012 or so).

 

[CBR.worm]

I have had a number of AWD vehicles over the years that vibrated or made noise at neutral throttle on the highway. I've never known what caused it - I always assumed lash or slop between all the u-joints, differentials, CV-joints, and transfer case chains, etc. when unloaded.

 

[metroplex]

I still have the same vibrations. Doing searches on CV Joints doesn't show any correlation with deceleration... Only acceleration. But this is the only forum that I've seen others mention CV joints could cause the vibes during decel. I don't hear any clicking while turning.

150 ft-lb IS the correct torque spec. Even dealerships get confused. These are 14mm studs, not your average 12mm or 1/2" studs. 110% confirmed they are 150 ft-lb. The lug wrench size is 21mm as well if that gives you an idea of how big the lug nuts are. There is even a door sticker that says to add 3 psi to the tires if you intend to drive over 100 mph. The only Ford I have seen this sticker on is the Ford GT. Not even my Mustang had this sticker.

 

[HankHill]

CV Axel. Joint is shot at either end. If your car was RWD, I would have said your driveshaft and U-Joints were the cause.

Every time I replace my U-Joints on any of my RWD cars, I have the drive shaft balanced at a local shop. You would be surprised that only one out of the five driveshafts I've had balanced was true. The rest weren't off by much, but they needed new weight.

 

[metroplex]

When I had bad U-joints with a RWD, it would always vibe badly under acceleration. I don't recall it doing it under neutral throttle/coasting deceleration.

I don't hear any clicking or thumping while turning, or getting on the gas while turning. Every video I've watched and article I've written said the CV joints would go bad when it would vibrate under acceleration/power or make the clicking noises. I only hear the thumping on deceleration at certain speeds (40-60 mph or so). It's smooth at 70+ mph.

 

[meep]

Engine mounts loose causing a shift and putting driveline at odd angles during decal?

shift to N and see if that changes?

 

[metroplex]

No change when shifting to Neutral. It still does it. When I use engine braking for decel it seems to go away. But that’s kind of like the same thing as applying power to the wheels

 

[Klarque420]

Check your wheel bearings

 

[PimTac]

Automatic or stick shift?

 

[Klarque420]

Automatic or stick shift?

All 2017-2019 Fusion Sports are 6-speed automatic.

 

[mk378]

Check that the bolts are tight on the driveshaft flanges.

 

[t1snwrbrdr12]

No change when shifting to Neutral. It still does it. When I use engine braking for decel it seems to go away. But that’s kind of like the same thing as applying power to the wheels

Not saying it’s CV joints, but that leads one to point that direction even more. Under accel or engine braking, the joints are under a load. If coasting they are not, which (I only skimmed this thread again so I may be misinterpreting) is when you are saying your vibration is.

 

[metroplex]

Not saying it’s CV joints, but that leads one to point that direction even more. Under accel or engine braking, the joints are under a load. If coasting they are not, which (I only skimmed this thread again so I may be misinterpreting) is when you are saying your vibration is.

Yes, it's only when coasting at certain speeds (like 40-60 mph). Feels fine at 70+ mph, even coasting. No sounds or vivbrations while turning, cornering, etc...