C70 vibrations
 

Hi, first off, i wanna apologize that my first post is basically straight to asking for help.

I have a 2011 C70 that’s developed some pretty heavy vibration. Its worst at 80km/h while the accelerator is pressed. If i ease off the gas at that point the vibration eases off. To me, this seems to imply a drivetrain problem. However, when i took it to the mechanic, he’s trying to convince me that its the suspension and he basically wants to change all the shocks and stabilizer links. Does this make any sense, or is he trying to get me to waste 2k on suspension?

it feels like when the cv boot was busted, but that was replaced last year and the mechanic said it still looks fine now.

Thanks. Any help appreciated.

Usually that is caused by a bad/worn cv joint in an axle. Usually the right axle wears out first.

+1. Doubt its suspension parts. Vibrations are caused by things that rotate, not things that go back and forth. Axles, wheel/tires, wheel bearings, motor mounts, brake rotors would be on my list - order depends on some other tests.

yeah that was my initial suspicion too. But on visual inspection, they seem fine. I may consider taking the cv joint boot off to inspect the actual linkage inside but i'll have to find another workshop first since i don't trust my usual workshop anymore.

Upon further testing, it seems to happen mostly around the 1500 to 2000 rpm range and not just at 80km/h like i initially thought.

if the vibration seems to be tied to engine speed vs roadspeed, that would move motor and transmission mounts further up my suspect list :-) I'd probably do a few more test drives to see if you can replicate. Have you worked with a buddy to see if the engine has some unusual sounds or movements when revving or even power-braking? Note: Safety first, don't do this in front of a garage or with your assistant standing in front of the car while you press the brake and gas at the same time.

I don’t recall there being *much* vibration when revving it in neutral. But i’ll check it again to be sure. Unfortunately i’m away for work right now so I won’t be able to test it again until this weekend.

Is it possible to check the conditions of the motor mounts without getting it up on a shop lift? Where are they and what would i be looking for?

also, could it possibly be the turbo? I’m assuming 1.5 - 2k is around the rpm range for the turbo to spool up. But could a faulty turbo cause engine vibrations? I’ve never dealt with a turbo unit before so i have no idea what to expect.

The right engine mount (at the front of the engine) can sag and cause vibrations - usually felt worse when first started cold. And not when driving @ 50 mph. You are in Asia - what engine is in your car?

The turbo spins all the time. It's not your turbo. At xx rpms the turbine blades are spinning fast enough to overcome the vacuum created in the engine (by the pistons sucking air in) which becomes boost stuffing more air and fuel in the cylinders - creating more HP.


Once again - a symptom of a worn outer cv joints is vibration when accelerating that stops when a steady speed is reached. To check for a worn cv joint requires dismantling the joint - a very messy job. You can't see a worn CV joint without taking it apart.

Ok, so I can confirm there is absolutely no vibration when revving it in neutral or when power-braking. So am I correct in assuming the problem should be coming from the cv joints?

my engine is the T5 from 2011.