Shake at high speed

[Kody Budinger]

After making the long trek back home for the holidays I noticed an obnoxious shaking at about 60mph when I was on the intestate. I knew I had a little mud on the tires and under the truck. After getting home I got all or most the mud off underneath took it for a drive and the horrible shaking went away but still noticed a little bit of shake from what seemed to be coming from my rear wheels. What could this be? Could my tires be out of balance?

 

[Andy Chase]

May need to balance and rotate. Might be something more severe, but it might be a good start. When I bought my F-150 I didn't go faster than 60mph on the test drive because of where it was, but on the way home I was doing 70 and the truck shook really bad. took it to my mechanic and he told me it was just because the tires were shot (I knew I needed to buy tires anyhow so luckily that's all it was). Got new tires and it hasn't done it since.

 

[Norm Reeves]

Check for a loose shock.......:grin:

 

[Rick Kent]

Could be the infamous drive shaft out of balance. But since you mentioned mud, you likely threw your wheels out of balance with all the mud. Clean them good.

 

[swshawaii]

Here's the drive shaft TSB. Only applies to 4x4 and 4:10 gearing between 75-80 MPH. Definitely inspect the tires and drive train first.

 

[Kody Budinger]

I cleaned the wheels and everything around them and the entire under body really well. I have 4:10 gearing... I really hope its not the drive shaft cause if it is it will be the third time my ST will have something broken in the last 2 months. :banghead:

 

[Yardsale]

That TSB does not provide the whole story, however, the speeds noted in the TSB are are about correct and are higher than you report. If it were the drive shaft, you should have noticed it long ago (it comes with the vehicle - a no-cost non-option).



There are some vibration diagnosis charts in my library Vibration Chart folder (http://mysporttrac.com/shared/memberlib.asp?view=10521&folder=Vibration%20Chart).



I think Andy is on track - check for tire abnormal wear, balance and rotate (might be due anyway).

 

[marlon giese]

I've had 2 sets of tires and get a vibration more like 82-85mph and higher. Any likelihood the driveline is the cause?

 

[Yardsale]

Read the TSB and vibration charts.



That range would be about right if the differential ratio is 3.83.