I've been feeling some vibration coming from the rear of the car only on deceleration. It pulls nice and smooth and there's no whining coming from the diff while under load or cruising. It feels almost like a belt separation in a tire but the tires are fine. I had them balanced and checked. It's most prominent around 45 mph in 3rd and 4th gear.

So I decided to look into it further. Upon removal of the prop shaft. I found gear oil on the prop shaft bolts and in the holes. The weird thing is there are absolutely no leaks coming from the diff. Not where the pinion bolt is not the pinion seal. It's strange. The oil is clean and the diff is topped off when I checked. Besides that weird finding, I am just wondering if anyone has had a similar issue with the slow vibration on decel only? Any insight would be appreciated.

Oil in the bolt hole

Oil on the prop shaft

Dry in there around the bolt

No leaks here

 

Vibration on deceleration is super common on 00-01/02 due to the friction disc in the clutch. It creates the well know “clutch buzz”. The 02-09 updated disc is gold.

Any hidden damage on the disc will have the same affect.

Another one is a car that has had a previous axle bucket swap. When the cups are reversed it causes decel vibration. Most dont feel it, as the vibration is less during coast.

 

The oil leak is inconsequential.

Dif oil, cv grease, or both can leak into that cavity.

Any leak is completely contained in the small cavity.

 

Broken/torn engine/trans/diff mounts would be good to check for

 

This one happened to me. Initially after bucket swap all was fine. Maybe 15k or so later, suddenly got this decel vibration.

Top down it was it always noticeable. But top up, it somehow created a resonance that could be quite dramatic at certain speeds in certain gears. Like shake the whole car feeling. Maybe I need to pull over right now feeling.

A simple set of axle spacers cured it. So now I'm cup swapped and spacered. Next time I get vibes I can swap cups back while keeping spacers. Another lifespan.

After that I'll need new cups.

 

Yes, sounds like CV cups were very heavily pittled and then swapped. Vibration on decel (esp. coasting/engine-braking) would then be very noticeable.

See the CV cup swap thread in my sig for pics of mild-to-severe pitting.

 

could be grease from the CV in the prop shaft leaking out. Could clean it up an inspect regularly to see where it shows up again.

Agree on either original clutch (if that is the case) or just feeling the decel version of the pitted cup vibration. I have not noticed it on my pitted and swapped units but it will depend on the severity and how closely you are paying attention. But, 45-70mph is pretty much where the frequency of the cup vibration makes itself noticeable so this kind of aligns with that.

 

Glad I bought some new OEM axle buckets a while back to install when the current ones become pitted. No swap, just remove and replace.

 

To be fair, same amount of work either way. And really should keep the bearings with the cups they have worn to (aka new cups, new bearings). Granted in a pinch plenty have run different cups with the existing bearings and not had issues. But as far as process you still have to remove the old cups, clean up the mess, grease and reinstall, so does not matter if using old or new ones. New ones just cost you money vs just the cost of new grease for swapping. If yours pit I would 100% swap them and save your new cups. Then if they pit again, put in spacers, then if again, swap back and keep the spacers, then IF they do it again, use your new cups. Get the most $$$ you can out of the existing ones!

 

Billman, I'm curious: have you seen the '00-'01 clutch buzz causing "whole car" shaking? My car had it and it was an infernal racket, but I wouldn't have said the car itself was shaking.