Downhill-gas off vibration

[koolaid81]

Alright I just finished driving my ex back out to CA from MN. Noticed while driving a horrible vibration when the car is going downhill... these conditions exsist:

1) downhill while cruise control uses engine for braking, it stops suddenly with little change in RPM

2) when driving downhill, release gas pedal, will vibrate for approx 15 seconds, then stops, speed independent

3) while driving downhill, release gas pedal, then shift into neutral, car still vibrates for approx 10 seconds prior to stopping

When I first felt it in June I thought it might be a U-joint and didn't investigate further, however the U-joints are fine. the vibration is higher frequency and as I said seems to be the same at 40 or 75 and at any RPM

EDIT: when I say "it" stops I am referring to the vibration

 

[doonze]

It's got the Explorer shakes! It's chronic and unfixable at this time, there is no known cure! Cash for Clunkers is the only current fix!

Well, at least so far this seems to be my case. These things seem to love to shake, due to about 100,000 different things. I don't think I've ever seen two people solve a shake on these using the same method. I think telling someone to change the dome light has about as much chance of fixing the issue as anything else!! LOL

But on a more serious note... have you checked the normal stuff, shocks? Bushings? (RA bushings would be top of my list) Bearings? Play in front end? How do you KNOW the u-joints are good? Engine mounts and tranny mounts? The down hill thing makes me think it's when A) the weight i shifted front, and B) the drive train has "back pressure".

Maybe the fact that going into neutral doesn't "stop" it is sympathetic shaking while the truck is fighting the shaking, until it's able to control it?

I still vote RA bushings as a top contender on the list.

 

[koolaid81]

the arm bushings huh? well they seemed solid enough, have yet to hear a peep from them but that is a good idea, the drive train back pressure was what I thought of immediately

-Martin