vibration during deceleration...

RichM

RichM

Registered User
I have a vibration that occurs or is amplified when I let off the gas. The vibration does not come though the brake peddle or gear shifter. Oh, it's a 5 speed. I really didn't notice the vibration till I changed tired, went from Michelin Pilot's to Kumho ASX. I have had the new tired balanced twice. The vibration seems to be coming from the rear of the car.

What areas should I be looking at when I get the car up on some jack stands?

Rich
 
RichM said:
I have a vibration that occurs or is amplified when I let off the gas. The vibration does not come though the brake peddle or gear shifter. Oh, it's a 5 speed. I really didn't notice the vibration till I changed tired, went from Michelin Pilot's to Kumho ASX. I have had the new tired balanced twice. The vibration seems to be coming from the rear of the car.

What areas should I be looking at when I get the car up on some jack stands?

Rich
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Check your U-joints front and back.

Check the bolts that hold the companion flange to the driveshaft.

Check the front differential mounting bushings.

Check for excessive on both halfshafts.

I had the same issue you are describing and it was the bolts that hold the driveshaft to the companion flange on the differential.
 
Jacked the car up and found a loose brake caliper. tightened up the caliper checked the u-joint to flange bolts at front of the differential. That made the vibration a lot less, but it isn't gone. Feels like an out of balance tire. I've had the tires balanced twice and will have it done again when I get the time.

I jacked the car up again and tightened the hell out of the differential bushings(not so much to crush them but made sure they where tight). I also replaced the rear differential mount (had a spare lying around). Took it out to get a burger and a six pack, sill has the vibration.
 
Have you moved the rear tires to the front and front to rear to see if the vibration moves? Tires shouldn't have an impact on acceleration or decel. They just change based on your actual speed.

How does it fill at cruise speeds? If the vibration is reduced at cruise, but there at decel and accel then the problem has to be in the driveline.
 
Mike, I have not swapped fronts to rear yet. I have thought about it though. That may happen tomorrow if I don't feel like cleaning the house.

The deceleration only vibration is the part that has me scratching my head until my scalp bleads. At cruise and acceleration the vibration is a lot less than during deceleration.


Mike8675309 said:
Have you moved the rear tires to the front and front to rear to see if the vibration moves? Tires shouldn't have an impact on acceleration or decel. They just change based on your actual speed.

How does it fill at cruise speeds? If the vibration is reduced at cruise, but there at decel and accel then the problem has to be in the driveline.
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I had the same problem on my 94. 3 out of 4 bolts on the pinion flange were crazy loose:eek: check the U-joints for play and the bolts on the flange (12mm 12point?)
Beyond that.... by deceleration do you mean actual braking or just lifting off of the throttle. Maybe a ram-rod with an impact warped your rotors when you got the new skins.....
 
BlkBirds said:
I had the same problem on my 94. 3 out of 4 bolts on the pinion flange were crazy loose:eek: check the U-joints for play and the bolts on the flange (12mm 12point?)
Beyond that.... by deceleration do you mean actual braking or just lifting off of the throttle. Maybe a ram-rod with an impact warped your rotors when you got the new skins.....
Click to expand...

Vibration is the same if I'm applying brake or if I just let off the throttle.
I'll double check the flange bolts tomorrow if I can.
 
When I had this mystery problem, it turned out to be the 4 bolts holding my drive shaft to the differential had shaken themselves loose. I had failed to apply loctite to them when I had the driveshaft off about 12 months earlier. :)
 
Make sure all brake caliper bolts are tight. The rear brake caliper bracket is prone to seizing the lower slide pin in the bracket. That could promote a braking vibration, but only if you hit the brakes usually.

Do you feel the vibration through your seat, through the steering wheel, through the shift lever, or all of the above?

A slight vibration under power and cruise, but more significant on decel or braking sounds like an issue related to changing pinion angle. Perhaps able to move more when under decel than when under power.

Check all the u-joints in the drive shaft and take a hard look at the bolts holding the diff in. maybe get a floor jack in under the diff and see if you can move it.
 
Mike8675309 said:
Make sure all brake caliper bolts are tight. The rear brake caliper bracket is prone to seizing the lower slide pin in the bracket. That could promote a braking vibration, but only if you hit the brakes usually.
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The vibration is not while braking, only when I let off the gas. The vibration is vehicle speed dependant not engine speed dependent, no mater what gear I'm in or if the tranny is in gear or clutch in or out.
I did find the passenger side rear caliper loose. After tightening it the vibration did not go away.

Mike8675309 said:
Do you feel the vibration through your seat, through the steering wheel, through the shift lever, or all of the above?
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Vibration is felt though my seat, Not the steering wheel or the shift lever or the brake pedal. I hear it more than feel it, it sounds to be coming from the rear.

Mike8675309 said:
A slight vibration under power and cruise, but more significant on decel or braking sounds like an issue related to changing pinion angle. Perhaps able to move more when under decel than when under power.
Click to expand...

No or very little vibration is felt or heard while under power or at cruise, only during deceleration.

Mike8675309 said:
Check all the u-joints in the drive shaft and take a hard look at the bolts holding the diff in. maybe get a floor jack in under the diff and see if you can move it.
Click to expand...

I did jack the differential up and noticed some seperation of the rear mount rubber. So I swaped it out from an old differential that was in much better condition. I also tightened up the mounting bolts for the differential as much as I dared without causing undo distortion of the polyurethane bushings.
 
Check your exhaust hangers. Check that the rubber is solid, and the brackets that mount to the car frame are tight. Pull and shake everything to see if it rattles anywhere. I have a frequent problem with the exhaust hanger bracket just below the driverside door. It works itself loose and develops a rattle that sound like something in the door istelf. It is more pronounced under acceleration. The solution was to cut off a small 1" square piece of an old bicycle inner tube, cut a hole in it and place it between the bracket and the car's frame. Its been quiet for about a week now. :D
 
I agree, if you're hearing it more than you feeling it, exhaust parts are certainly something to take a look at. I wish you luck.
 
do you feel the vibration in the seat, if so its the driveshaft. the bolts that attached to the differential might be loose. use loctite and tighten the bolts and see what happens.:)
 
Thanks for the followup.

You should feel the vibration coming out of my winter beater ranger. A u-joint froze up in it about 3 weeks ago. I'm to busy to have the truck down right now so I've been driving it. The center bearing on the shaft is junk and it shakes pretty good until I get up to about 45mph. I've got a complete spare driveshaft with u-joints in my shed, but it's way in the back and I haven't been willing to dig it out yet.
 
Mike8675309 said:
Thanks for the followup.

You should feel the vibration coming out of my winter beater ranger. A u-joint froze up in it about 3 weeks ago. I'm to busy to have the truck down right now so I've been driving it. The center bearing on the shaft is junk and it shakes pretty good until I get up to about 45mph. I've got a complete spare driveshaft with u-joints in my shed, but it's way in the back and I haven't been willing to dig it out yet.
Click to expand...

I feel your pain Mike. I wimped out, I dusted off the motorcycle and took the T-bird to one of the better local shops and had them replace the U-joints. That was after tightening every bolt and bushing in the rear. Which had me so pissed it wasn't funny.
 
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