Random steering shimmy - can't figure it out

[rivetc78]

My '08 Ranger with coils in the front has developed a weird, random steering shimmy at speeds over 50mph. It comes and goes and is never at a constant speed. It seems to get more violent at higher speeds however. It's at the point where I have to stay off freeways because I can't hold the wheel over 65. I have done the following, all to no avail:
- balanced all tires twice at 2 different shops including static on the vehicle at Ford
- front end alignment
- new lower ball joints
- new outer tie rod ends
- new stabilizer bar bushings
- new stabilizer bar end links
- front bearings removed and re-packed with grease and checked twice for lateral play
- The shocks were replaced last fall but I remember one of the front ones feeling "different" when I primed them.
- Front end inspection at mechanic with everything being reported as "tight"
- I've jacked up the front and checked everything myself including checking for wheel play horizontally, vertically, laterally, etc.

I'm stumped!!!

 

[rivetc78]

Update: according to the Ford diagnostic flow chart for this condition, shocks may be the cause. I've since put 4 new KYB shocks but the problem persists...

 

[pjtoledo]

stock size wheels & tires?
do tires have a wear pattern?

calipers move ok?

 

[monstermazda]

Wheels unbalanced can cause this and rack and pionion going out can cause this to

Sent from my SAMSUNG-SM-G870A using Tapatalk

 

[rivetc78]

I am currently running MB wheels with BF Goodrich All Terrain T/A's on it. Stock size. They are wearing properly. I have had them re-balanced and the front end re-aligned. Mileage on the vehicle is 90,000 miles and tires is 40,000 miles. The strange thing why I think it's not tires is that the vibration is not constant. It seems to be generated after hitting a bump or driving around a bend in the highway. I thought maybe wheel bearings but they are not "growling" and there is no play in the wheel when jacked up. I double checked the tightness of the castle nut and it is good.

 

[rivetc78]

In response to the caliper a question, I took them out and put in new slide pins with brake grease on them so they are functioning perfectly.

 

[rivetc78]

Another update: I had the power steering fluid flushed at Ford thinking maybe air in the system could cause it. No change.

 

[alwaysFlOoReD]

The wheels could be balanced and still be out of round.

 

[rivetc78]

Would wheels out of round shake 100% of the time? I ask because this vibration comes and goes?

 

[alwaysFlOoReD]

My personal experience is that at very slow speeds it's noticeable [under 5 mph]. Then it at higher speeds it depends. Try swapping front and back tires.

 

[adsm08]

It could also be a road-force issue.

Road-Force is when varying spring rates in the tire sidewall cause an effect similar to the wheel being out of round but it can change based on road surface, speed, tire temp, air pressure, and can come and go with turns.

My wife's Explorer had a nasty front end vibration that behaved much like you describe. While I can't prove it I think it was that the two front tires had excessive road-force and the high spot were coming in and out of phase with each other as we went through bends and curves on the road.

 

[rivetc78]

I swapped the tires front and back and still the problem persists. It seems to be occurring more at lower speeds now. Driving this morning at 50mph, the vibration appeared a few times; most noticeably after hitting a bump in the road.

 

[pjtoledo]

I am currently running MB wheels with BF Goodrich All Terrain T/A's on it. Stock size. They are wearing properly. I have had them re-balanced and the front end re-aligned. Mileage on the vehicle is 90,000 miles and tires is 40,000 miles. The strange thing why I think it's not tires is that the vibration is not constant. It seems to be generated after hitting a bump or driving around a bend in the highway. I thought maybe wheel bearings but they are not "growling" and there is no play in the wheel when jacked up. I double checked the tightness of the castle nut and it is good.

what is the size and offset on those wheels?

did you inspect the spindle shaft for wear when bearings were serviced?
its rare, but the inner race of each bearing can slowly turn on the spindle shaft.
that wears the shaft, when it gets bad the bearing can wobble on the shaft.

 

[rivetc78]

So I took the rotors off and re-inspected the bearings, spindle shaft and races and everything is in great shape. Also, I just had new tires put on today as they were the only item I couldn't confirm 100%. The vibration is still there. Again, it comes and goes and is not constant. I can be driving at 60mph, smooth as silk, hit a bump and the steering wheel starts to shake. I am truly stumped with this one!

 

[rivetc78]

Problem Solved!!!

It could also be a road-force issue.

Road-Force is when varying spring rates in the tire sidewall cause an effect similar to the wheel being out of round but it can change based on road surface, speed, tire temp, air pressure, and can come and go with turns.

My wife's Explorer had a nasty front end vibration that behaved much like you describe. While I can't prove it I think it was that the two front tires had excessive road-force and the high spot were coming in and out of phase with each other as we went through bends and curves on the road.

Since I had tried almost everything else, I brought the truck in this morning to a different shop and had all 4 tires road-force balanced. On this machine, I was told that they were all out of balance despite being brand new and "laser balanced". Took the truck on the freeway and... Smooth as silk! I had never heard of road force balancing until adms08 mentioned it. I am now that much smarter! Thanks adms08!!!!!