Weird vibration. I would like help. Rx8

Did all the work.  Angles look great.

Vibration still exists.

Ermagawd.

Maybe it just needs to be broken in harder? 

Ooooof. Frustrating. Driveshaft couldn't be bent or slightly out of phase?

Robbie (Forum Supporter) said:

Ooooof. Frustrating. Driveshaft couldn't be bent or slightly out of phase?

This is driveshaft #2.

I'm tearing my hair out in empathy.

Oops, no, I'm just balding.

But still...

There has to be a reason, or reasons. I'm sorry finding and fixing it is so maddening. I know at some level it would bug me to tear it apart and rework the whole thing and never know what the issue was. Though that would still be better than having the issue...

I can say after driving it 300 miles to Gainesville last night that it REALLY doesn't like 60mph.  Everything before about 57mph is fine.  Everything above about 63mph is virtually fine.  You can still feel a little "buzzing", but it's not that noticeable. 

In reply to wvumtnbkr :

Well, that's progress? A lot better for that speed to be the issue than 70!

wvumtnbkr said:

I can say after driving it 300 miles to Gainesville last night that it REALLY doesn't like 60mph.  Everything before about 57mph is fine.  Everything above about 63mph is virtually fine.  You can still feel a little "buzzing", but it's not that noticeable. 

That's what my truck was like. It was manageable if I could avoid those speeds, which I mostly did. It was also worse with every wheel except the factory ones.

I know you changed the driveshaft but did you change the U-joints?

Had a similar vibration on my MDX. Tried other wheels and tires (no difference), ran it on a lift to listen for wheel bearing noise (no) and started worrying it was a transmission / transfer case / differential issue.

Removed the rear driveshaft to drive it in FWD mode to see if the problem went away and noticed that the rear U-joint was nearly seized. U-joint is welded on and non-serviceable, but a replacement driveshaft fixed the problem.

Okay...  today my neighbor and I jacked up the car and put about 15 jackstands underneath it.

He ran the car up to the trouble speed (57 to about 64).  Vibration was definitely present.

I took the rear wheels off and ran the lugnuts back down to keep the rotors on.  Vibration was still present.

I took the rotors off and ran it back up to speed.  Vibration was still present.

I took a screw driver and touched it to different parts to see if I could "feel" the Vibration.

Both hubs felt like they weren't even moving they were so smooth.

Ppf had no Vibration.  Driveshaft has no wobble and I couldn't feel any Vibration (screwdriver on side of driveshaft).

Axles didn't feel like much Vibration and they felt equal.

Nose of diff felt as smooth as the hubs.

The back of diff was vibrating enough to "bounce" the screwdriver off of it.  Huh.

So is that a bad inner cv joint, or something fubared with the diff itself?

Anybody have any ideas on how to test further?  My only thought is that I could disassemble the rear axles and reinstall just the stub shafts. See if that does anything.  If the Vibration is still present, it means it's diff or driveshaft.  If it's gone it means it's axle or hub.

That's a lot of work that I'd rather not do if there is a better way to diagnose.

Okay...  today my neighbor and I jacked up the car and put about 15 jackstands underneath it.

He ran the car up to the trouble speed (57 to about 64).  Vibration was definitely present.

I took the rear wheels off and ran the lugnuts back down to keep the rotors on.  Vibration was still present.

I took the rotors off and ran it back up to speed.  Vibration was still present.

I took a screw driver and touched it to different parts to see if I could "feel" the Vibration.

Both hubs felt like they weren't even moving they were so smooth.

Ppf had no Vibration.  Driveshaft has no wobble and I couldn't feel any Vibration (screwdriver on side of driveshaft).

Axles didn't feel like much Vibration and they felt equal.

Nose of diff felt as smooth as the hubs.

The back of diff was vibrating enough to "bounce" the screwdriver off of it.  Huh.

So is that a bad inner cv joint, or something fubared with the diff itself?

Anybody have any ideas on how to test further?  My only thought is that I could disassemble the rear axles and reinstall just the stub shafts. See if that does anything.  If the Vibration is still present, it means it's diff or driveshaft.  If it's gone it means it's axle or hub.

That's a lot of work that I'd rather not do if there is a better way to diagnose.

blacksheep said:

I know you changed the driveshaft but did you change the U-joints?

Had a similar vibration on my MDX. Tried other wheels and tires (no difference), ran it on a lift to listen for wheel bearing noise (no) and started worrying it was a transmission / transfer case / differential issue.

Removed the rear driveshaft to drive it in FWD mode to see if the problem went away and noticed that the rear U-joint was nearly seized. U-joint is welded on and non-serviceable, but a replacement driveshaft fixed the problem.

Yes, new u joints.

It does sound like a diff or CV issue now, usually you don't get any significant vibrations from CVs before they fail in my experience. Before my Toyobaru's left inner CV blew up on the highway there was just a few seconds of almost unnoticeably subtle vibration before it happened.

QuasiMofo (John Brown) said:

Listed as for automatic only.  I also think they are different left and right, but I'm willing to try it!

Any chance you have a lathe or a way to make a plug, then pull out one axle at a time for testing?  If you pull both and it still does it, it's the diff:)

WonkoTheSane said:

Any chance you have a lathe or a way to make a plug, then pull out one axle at a time for testing?  If you pull both and it still does it, it's the diff:)

I'm kinda wondering if I can just pull both and see what happens.  

wvumtnbkr said:

WonkoTheSane said:

Any chance you have a lathe or a way to make a plug, then pull out one axle at a time for testing?  If you pull both and it still does it, it's the diff:)

I'm kinda wondering if I can just pull both and see what happens.  

Isn't the worst thing that can happen is you just make a mess of gear oil? 

peanutpckrupper said:

wvumtnbkr said:

WonkoTheSane said:

Any chance you have a lathe or a way to make a plug, then pull out one axle at a time for testing?  If you pull both and it still does it, it's the diff:)

I'm kinda wondering if I can just pull both and see what happens.  

Isn't the worst thing that can happen is you just make a mess of gear oil? 

Aren't all the moving parts on the inside?  Could you just use a little tape to reduce the splash?

wae said:

peanutpckrupper said:

wvumtnbkr said:

WonkoTheSane said:

Any chance you have a lathe or a way to make a plug, then pull out one axle at a time for testing?  If you pull both and it still does it, it's the diff:)

I'm kinda wondering if I can just pull both and see what happens.  

Isn't the worst thing that can happen is you just make a mess of gear oil? 

Aren't all the moving parts on the inside?  Could you just use a little tape to reduce the splash?

Good point... My plug idea was just for the oil, for this test I'll bet duct tape would work fine...

Sounds like you are on the right track. While you are in there, check the differential and subframe mounts. If they weren't bad before, all the vibration may have affected them.

I ordered an axle.  We will see if it fits.

I am wondering if the diff "needs" the axle stubs inside the assembly for any reason.

I can totally plug the holes with some gorilla tape if not.

This is annoying enough that I don't like driving the car.  Need to fix this!

Either way, the axles are coming out and then I'll see if there is anything obvious.

wvumtnbkr said:

I am wondering if the diff "needs" the axle stubs inside the assembly for any reason.

I have very little experience with differentials, but for the one I have worked on, if you were to pull both axles, the ring gear would drop down. I infer from WonkoTheSane's question about a lathe that this is the case for many diffs. 

Rx8 axles are NOT the same left and right.

Drivers side on the left.  Bout 1.5 inches different.

All 4 of these joints are leak free, feel smooth.  Have no slop.

In reply to wvumtnbkr :

How hard is it to take the boots off and just put the CV cups in?