04 XC70 vibration/shaking/knocking

[nicklusnia]

I recently made a 250 mile/5 hour road trip with my 04 XC70 and once I made it to my destination I stopped for gas and when I pulled out I started to get a violent vibration and occasional knocking that feels like it is coming from the center front of the car. It started to only happen when I was getting up to speed while on an upward grade but seemed to happen at lower speeds and felt like she wasn't getting enough power a couple days later but a week later and it seems to be happening at slow speeds and low rpms on residential streets and now I can feel/hear more of a rotational slight knock at slow speeds under the car. When I let off the gas the shaking/vibrating stops but I dont even feel comfortable taking the car out at all. I changed the upper engine mount because I knew that was a common issue but that changed nothing. Researching it seems that the CVs have been the most common culprit but I have checked and had a buddy who is more car knowledgeable than me double check and the fronts seem just fine, there is slight give in the rears but it is an equal amount on both sides but the boots seem fine and nothing is leaking. Driving it just a few blocks today it seemed like I could hear and feel it a little more on the passengers side but I cant tell I might just be going crazy. Is it possible that the U joint on the drive train is out of balance or needs changing? or possibly engine mounts somewhere else need to be changed? Or is biting the bullet and changing the CVs the way to go? Is there an other issue I might be missing? seems that the vibration and knocking has gotten worse since it first started. It does have a lift and bigger tires but had an alignment no more than a week before the issue started and I dont feel the vibration in the steering wheel but you can very much feel it in the car. Thanks, I dont post on forums much so not sure if i need to give more info but gladly will.

[pbierre]

The first decision tree branch: If you just sit parked and run engine RPMs up to 3500 and back down, does it induce any vibration? Can you rapidly build RPMs from idle to 3500 and have it be smooth? This is a way to detect (or rule out) imbalance that originates in the engine, or engine mount system.

Next, to rule out any transmission problem, you can go to a hilly area, and using the manual shifter, evaluate all 6 gears for vibration.

If it's a drivetrain problem, you can begin by jacking up the car to lift all 4 wheels off the ground. In neutral, engine off, manually rotate one wheel at a time to evaluate any hysteresis or clunking sound. In this test, you are inducing a "reflected" load torque on the axle/drivetrain. This sounds like the condition needed for vibration, e.g., there is no problem when coasting.

-------Oversized tires ------------------------------------------------

I've written elsewhere how putting oversized tires on a car overloads the drivetrain with excess reflected torque. See:

https://forums.swedespeed.com/showth...0-P3-2008-2016

[NTXC]

Any engine lights on? Can you do a scan?

I was under powered and shaking pretty good for about 5 minutes before my check engine light came on, turns out I was getting cylinder misfires due to a failed ignition coil.

Basically I’m trying to help you and other posters figure out if this is a drivetrain issue, or if you’re having an engine problem as the description currently doesn’t lend to either in a straightforward way. If you didn’t mention being underpowered I’d think something like an axle.

[hoonk]

when I pulled out I started to get a violent vibration and occasional knocking

It started to only happen when I was getting up to speed while on an upward grade but seemed to happen at lower speeds

When I let off the gas the shaking/vibrating stops

feel it a little more on the passengers side

It does have a lift and bigger tires

Your symptoms sound like a worn/bad inner cv joint (actually a tripod cv joint)on the right side. Vibration when accelerating, stops when you let up on the gas, and the right side usually wears first.

That lift is probably not helping with the change of angles either.

I would look for a GKN axle. They are more expensive - but you will get very frustrated trying to find a cheap chinese axle that's not worse than the one you are taking out. GKN made the original axles in your car but are sold on the aftermarket. fcp, europarts, and many others carry them.

[Oro-o]

Your symptoms sound like a worn/bad inner cv joint (actually a tripod cv joint)on the right side. Vibration when accelerating, stops when you let up on the gas, and the right side usually wears first.

That lift is probably not helping with the change of angles either.

Sure does sound like that. A sudden on-set argues for something engine electrical like a coil, but the symptoms sound like a sudden failure here.

It does have a lift and bigger tires

This is a death sentence for a lot of CV axles...

Have you tried riding in the passenger seat while someone else drives? You can find/hear/feel things you cannot from the driver's.

Bear with me for an example: We have a Lexus and for several months I was searching for a few missing MPGs, no other symptoms I felt when driving (albeit not my daily driver, another family member). Finally one night we were out and I had a few glasses of wine, and let someone else drive. My feet felt vibration in the passenger seat floorboard not at all detectable from the driver's. Very soon I went to test the bearing and they were rough on that side. When replacing that I pulled the passenger side axle for inspection. The tripod joint came out literally in pieces; the only thing keeping it vaguely intact was that it was till in the soup can and the parts had no where to go. Coincidentally, this Lexus uses a variant of the Aisin 5-speed same as the XC, though albeit w/o the Volvo angle gear interface.

I go into that detail to say that a cursory inspection of either CV shaft w/o removal won't necessarily find a disintegrated inner CV joint. Your symptoms and the fact the car has the double whammy of oversize tires and lift argue to look at that harder.