Vibration / rumble when decellerating > 55mph

S

sail7seas

Registered User
I get a vibration with a rumble sound when I decellerate (lift off throttle).
This occurs any time above say 55mph. For example 70 mph down to 55 mph.
or say 80 mph down to 55 mph, I have put it in neutral with AOD @ 70 mph, and it still does it.

5000 miles ago 'Mr. Transmission' put in 3.55 gears & rebuild kit.
The noise is getting louder. 'Mr. T' says it is not the U-joints & all bolts are tight.
'Mr. T' says he is stumped. Motor mounts where replaced a couple of years ago to solids.
Any Ideas? :confused:
 
sail7seas said:
I get a vibration with a rumble sound when I decellerate (lift off throttle).
This occurs any time above say 55mph. For example 70 mph down to 55 mph.
or say 80 mph down to 55 mph, I have put it in neutral with AOD @ 70 mph, and it still does it.

5000 miles ago 'Mr. Transmission' put in 3.55 gears & rebuild kit.
The noise is getting louder. 'Mr. T' says it is not the U-joints & all bolts are tight.
'Mr. T' says he is stumped. Motor mounts where replaced a couple of years ago to solids.
Any Ideas? :confused:
Click to expand...

I had the same thing on the mustang. I too was stumped until I slammed 2nd and blew the u-joint. I bought a new alum. driveshaft from Ford Racing and the problem was fixed. Nice and smooth now. You may also want to try taking the driveshaft to diff bolts out and turning the shaft one way or the other by one bolt hole. I know the drive shaft is supposed to be marked and reinstalled in the same position as it was in from the factory.
 
trife86 said:
i had that problem too my wheels were unbalanced
Click to expand...
Are you serious? Is it something as simple as this.
Wouldn't unbalanced tires+wheels vibrate all the time vs only when off the throttle?
 
Had the exact same problem you are describing, I got under the car and I noticed that the driveshaft bolts to the rear dif were loose. Tightened them up and was driving as smooth as ever.
 
well how mine would do it if i go from a stop to whatever speed 60+ and not lift off its soo sooo smooth, i can do 100mph very smooth as soon as i lift off, vibration from hell and if i get back on the gas it will stay vibrating
 
90coug said:
Had the exact same problem you are describing, I got under the car and I noticed that the driveshaft bolts to the rear dif were loose. Tightened them up and was driving as smooth as ever.
Click to expand...


same here. Two of the bolts had almost backed out.
 
SLP007 said:
same here. Two of the bolts had almost backed out.
Click to expand...

Well, I told 'Mr. T' it was the bolts, from my research here. Yesterday, he said he check them and they were O.K.
Today, he just called me and he said the bolts were loose, and it is o.k. now.
Mr. T said he felt stupid, after he rechecked the bolts and they were loose.
I had visions of another 500-1000 dropped down the hole, just relieved he found it, and it was something simple.
Thanks, guys for the support. :) What a great website!
 
Very common problem...

I have seen too many people NOT tighten those bolts properly. Usually this is due to not having the proper wrench to do it with (torque of otherwise).

Make sure to drive it and check to make sure it is all ok now.


Good luck,

P.S. This site is AWESOME.!!!!!


7 years and still learning!!!


Don
 
sail7seas said:
Are you serious? Is it something as simple as this.
Wouldn't unbalanced tires+wheels vibrate all the time vs only when off the throttle?
Click to expand...

YES but the normal vibration from the motor reving up will tend to mask it while speeding up.
 
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