2012 C70 death wobble while accelerating, ~40MPH Topic is solved

Post by **Brucebo** » 27 Jul 2024, 17:35

My 2012 C70 recently started death wobbling around 40 mph, ONLY while under acceleration, or while the engine is under load, like going uphill. Immediately stops if I let off the accelerator. Engine sounds fine.

No wobble at any speed while coasting.

Suspension seems tight. No clunking or rattling.
Control arms are only a couple years old.
Sway bar end links, tie rod ends, ball joints, bushings all look good.

Don't hear any bearing noise.

Replaced both left and right engine mounts. Left was worn out. Didn't help.
Rotated tires. Didn't help.

Any ideas?

Post by **matthew1** » 27 Jul 2024, 17:48

Front wheels lug nuts tight?

MotorTheresa · Post by **MotorTheresa** » 28 Jul 2024, 00:26

CV shafts OK? Inner CV joints excessive play maybe?

AVOIT17 · Post by **AVOIT17** » 28 Jul 2024, 08:42

MotorTheresa wrote: ↑28 Jul 2024, 00:26 CV shafts OK? Inner CV joints excessive play maybe?

That is the first thing I thought : CV Joints.

Since it only happens under load it seem that it must be a powertrain shaft-joint of some kind...

Post by **Krons** » 29 Jul 2024, 17:37

Another vote for CV shafts.

Post by **Brucebo** » 10 Aug 2024, 12:52

Further update. The right axle is looking like the source of the problem, but I can't say for sure as I haven't replaced it yet.
Right inner boot has a small hole. The car is 12 years old and axles look original, with the "Volvo" label still visible. Since the car is lifted and the tires are "drooping" the CV joints are at a high angle. When I rotate the tire by hand the required torque gets noticeably higher at a specific tire rotation angle. I marked the tire and then turned it by hand without looking. When I felt the torque increase, the mark was back in the same spot. This could definitely drive a resonance at certain speeds.

Post by **MoVolvos** » 10 Aug 2024, 19:58

Brucebo wrote: ↑10 Aug 2024, 12:52 Further update. The right axle is looking like the source of the problem, but I can't say for sure as I haven't replaced it yet.
Right inner boot has a small hole. The car is 12 years old and axles look original, with the "Volvo" label still visible. Since the car is lifted and the tires are "drooping" the CV joints are at a high angle. When I rotate the tire by hand the required torque gets noticeably higher at a specific tire rotation angle. I marked the tire and then turned it by hand without looking. When I felt the torque increase, the mark was back in the same spot. This could definitely drive a resonance at certain speeds.

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2009 S60 2.5T AWD

Have not seen the car for about 7 months as it was at school out of State with one of the kids. Due to lack of time removing the axle, I did a grease repack and temp mending of the boot before sending it off in Jan.

Temp Axle Boot Mending
viewtopic.php?p=640597&hilit=2009+S60#p640597

After dropping a bag of CV grease from the Inner & Outer boot kit from FCP, the vibration and noise lessened. When trying the car yesterday I noticed a very slight vibration and noise but both were greatly, greatly reduced on the stretches of freeway that were newly paved. Unless it's newly paved roads I have the exact same symptoms as yours with more noise than the death wobble vibration. I didn't see a drop of grease from the temp mending. Probably broken for sometime before I acquired the car in mid Dec 23.

You might want to consider using a grease gun with a needle and injecting some grease directly into the bearing to see if the symptoms lessen? I used the needle to rejuvenate unbroken but old tie rod ends, sway bar links and ball joints. The suspension feels very quick and smooth afterward. Inject the CV boot at 12, 3, 6 and 9 o'clock and massage outside of boot to push in grease. Some will leak out with use but just wrap the hole with the wire loom double sided self sticking tape per Temp Mending link.
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5pcs Grease Needle Nozzle, Bearing Grease Injector Needle with NPT Threaded Narrow Needle Adapter Grease Gun Tip Dispenser Fitting Tool for Injecting Grease into Small and Confined Spaces
https://www.amazon.com/XIHIRCD-Injector ... ive&sr=1-8
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Post by **Brucebo** » 17 Aug 2024, 19:49

Epilogue

Replaced the right front CV axle today. PROBLEM FIXED!!!!!

Inner CV joint on old axle definitely has issues. I can not angle it freely with my hand. Seems to jam at certain positions.

Post by **Brucebo** » 18 Aug 2024, 20:20

Epilogue, part 2.

As I mentioned previously, the boot on the bad joint had a small, 1cm long split near the bottom of the wide section of the boot. I cut off the boot today and examined the joint. It was essentially dry. The metal had a film of grease on it, but there was no bulk grease in the joint. Looks like it had all been flung out over time through the little hole.

Post by **MoVolvos** » 20 Aug 2024, 13:44

Brucebo wrote: ↑18 Aug 2024, 20:20 Epilogue, part 2.

As I mentioned previously, the boot on the bad joint had a small, 1cm long split near the bottom of the wide section of the boot. I cut off the boot today and examined the joint. It was essentially dry. The metal had a film of grease on it, but there was no bulk grease in the joint. Looks like it had all been flung out over time through the little hole.

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Thanks for the update! Could you provide a link to the right axle purchased?
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