Highway vibration
 

I've been experiencing and trying to chase down a bad vibration at highway cruising speeds, 65-75mph. The vibration is not wheel balancing. I"ve rebalanced and rotated 2 different sets of wheels with no change. I think it's the driver side rear, definitely in the rear of the car since no vibration through the steering wheel.

Swapped the axle cups. Cups looked okay, but had no effect on the vibration.

I also noticed a big vibration/clunk in right hand turns at the racetrack. That's what led me to believe that it was axle cups, but haven't had a chance to see if it fixed that issue (haven't got out to the track since).

Any suggestions on where else to look and try? Maybe replace the whole axle?
Thanks!

i had a vibration at those speeds, it was a loose pinion nut on the diff.

drain your diff fluid, see if there is noticeable metal, like i had. that would be a sign.

If the axle cups looked good and swapping sides did not fix it I would not go right to replacing them. If you replace them you pretty much want OEM. Lots of garbage aftermarket axles out there from what I gather on the forums.

The vibration from the CV joints in the axles typically will be only under load (aka accelerating) and normally starts around 45mph. It sounds like yours is more constant?

Dont just rule out wheel balance just because you had them rebalanced. I had a wheel on a vehicle I could take back for rebalancing all I wanted, and they would say it was balanced. Still vibrated on the vehicle. Attempted to deal with it over numerous years with two different sets of tires. Put other wheels on, vibration gone. If you have access to another set of rears that would fit on your car, it is worth at least trying to eliminate wheels or tires

diff bushings, there are four of them, see if one has leaked onto exaust near diff.

A bent wheel can be balanced out but can possibly cause a vibration. A tire deformation perhaps as well. The balance machine can show if your tire/wheel wanders.

Let us know what you find out.

I've tried 2 sets of wheels already. I have a set of pf01 enkeis that I rebalance and rotated (square setup) and made no difference. Put my stock set on and while the vibration wasnt as pronounced, it was still there.

Picked up a new aftermarket axle from a buddy to try. Now it's got a new vibration! Lol! Most likely due to being aftermarket, it's got a power on vibration above 40mph. Still slight vibration on the highway. Thinking about trying to source a used or rebuilt OEM axle next.

Thanks guys. Definitely appreciate the ideas!

Damn, hopefully you find out what's going on.

power on acceleration above 40 is almost definitely a pitted CV bucket on the new axle you got. That is the number one symptom of that.

For your other vibration, does it continue if you hold in the clutch and coast or does it go away as soon as you do that?

Quick update. Replaced both axels with known good OEM units (both sides) and no change. Replaced driver side knuckle, no change after that either. Running out of ideas! Haha! Going to try and play with tire pressure to see if that has any effect. Also going to remove the CR wing. Maybe some sort of aero buffeting? Trying anything at this point.

And to answer the question above, it vibrates with the clutch in coasting as well. Wondering if it's the tires? Running Federal rsrr, but weird that it only effects the rear and no the front.