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Discussion Starter · #1 ·
Hi all,

/2007 S40 2.4i 165k miles/

I recently had to replace my front right cv axle, due to a shot carrier bearing. I have a vibration problem with this car since day one (bought it three years ago) and I never could figure out what's causing it. I tried to get rid of the vibration by replacing tires and rims as well and nothing solved my problem. Now that I had to replace the drive shaft, I thought it is the right time to debug what is going on here. The first thing I've done is that I bought an aftermarket CV shaft (I know, I know...) and I removed the OEM one. I felt the improvement and for a couple of days I had close to no vibrations, so I thought it was the passenger side cv axle and the problem is solved. However, the vibration came back not so long after and it is getting worse. I've removed wheel and I've jacked up the car under the LCA roughly to riding position of the joints and watched the shaft. Here is a video about it:

https://drive.google.com/file/d/1rONArIkmZLNX8qmgZxjHMKpvDPwSxWXu/view?usp=sharing

It seemed to be bent. I was thinking what can bend a new shaft and I came to the conclusion the if the carrier bearing is fixed to the chassis and cannot move, the other end of the shaft moved somehow. I thought that I might have a shot motor mount, because that would allow the hollow shaft in the tranny to move back and forth as the torque comes and goes during shifting. I've removed the motor mount at the passenger side and there there you go, it was shot.

I was curious to see whether the OEM cv shaft is bent as well. Today I've disassembled it at the inner joint and spun it in a lathe.

https://drive.google.com/file/d/13atoioJxrwynbPTzcn7_ghv6IBhZVVy9/view?usp=sharing
https://drive.google.com/file/d/14acKFMgi-QXS30kui_8TL1oeF8msAbKs/view?usp=sharing

This explains why I feel vibration, because all that wobble gets transferred to the chassis through the carrier bearing housing. It also explains why my carrier bearing failed. The carrier bearing of my new shaft heats up to close to 100 degrees Celsius when I drive the car. And that has to be due to the dynamic force generated by the wobble to the bearing.

In terms of what bends my shafts, I'm unsure whether the culprit was the motor mount or something else.
Any thoughts on what else might have caused this?

Thanks.
 

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A bad motor mount will put stress on the CV joints since it allows the engine and transmission to sit lower or even skewed.
 

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Thanks for this valuable info. Is the motor mount difficult to replace oneself or would one need a workshop to do it? Any video done on replacement of this mount because I may have a similar vibration problem but I need to know where to start looking and identify the problem.

Sent from my SM-G960F using Tapatalk
 

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Discussion Starter · #6 ·
I've ended up replacing both upper motor mounts (left & right). The OEM torque mount is also replaced with an e-focus mount. I'm going to try to straighten the original OEM axle. If I don't succeed (very likely), I'll get an another OEM axle from a junk yard. Other than a loose motor mount I have no idea what else can cause this.
 

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I have the same exact vehicle as you but much less mileage at 42k. I tried this last summer to get rid of the vibration in it as well.

I have all new motor mounts and purchased brand new wheels, and the tires only have 4k miles on them. I road forced balanced the tires and the car still vibrates somewhat at highway speed. Axles are OEM as well (the originals were replaced as part of a TSB with an improved version)

I think these cars will never be perfect. A combination of a lot of different design features or lack of good tolerances I think.
 

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So in tracing down this issue - I have replaced everything on both front sides of the car:
Strut assembly
Knuckle
Bearing
LCA
Rotor
Axle
2 sets of tires
I have wire brushed the bearing face and the rotor cap inside and out.
Only thing NOT new on both sides of the front end was brake pads and endlinks.

Oddly - this problem only started showing up when I switched from my CLAVA (winter) wheels to my oem summer wheels (forgot their name). I switch back and the problem completely goes away. I had the rim specific to this issue examined, and was not determined to be an issue (out of round or bent in any way). All wheels road force balance correctly.

Problem is still there oddlyuntil I heat up the brakes pretty good, then it is completely gone until they cool again.

Occams razor suggest it's the pads. at this point, while I have never run into a situation where the pads create different torque values on either side to the point of causing a single wheel shudder while braking - it's gotta be them.
 

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Oddly - this problem only started showing up when I switched from my CLAVA (winter) wheels to my oem summer wheels (forgot their name). I switch back and the problem completely goes away.
What wheels, specifically? I'm guessing they're a different offset. The front suspension is quite sensitive to geometry, and changing the offset moves the center of the contact patch, which in turn changes the scrub radius. This can cause any number of interesting effects.
 

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What wheels, specifically? I'm guessing they're a different offset. The front suspension is quite sensitive to geometry, and changing the offset moves the center of the contact patch, which in turn changes the scrub radius. This can cause any number of interesting effects.
https://parts.volvocarslisle.com/a/...1957_5704684/Aluminium-rims-16/GR-317103.html
#9 on this page. Supposedly came off a V50 - but don't know the history before that. 16" stock size like my Clavas. Don't know why just ONE wheel would have this issue which is what makes it so odd. I should mention vibration doesn't follow that wheel either when I move it around the car.
 

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Hrm, interesting. So I popped off the cap of the rim and looked inside. Sure enough, there is a GAP between the center of the rim and the outer ring of the bearing hub.
Not exactly shocked. Dude told me he was coming down that day from Vail and ended up being over 2 hours away from Denver to pick them up, so it doesn't shock me if he had rings and didn't include them or just assumed that's how a volvo drives.

That being said, that is definitely the source of my issue. I guess when I switch to winters I'll take measurements and get some hubcentric rings on order for summer there to manage the load better. Thank you for the suggestion, I was about at my wit's end with this one.

Stock S40 bearing outer surface is 63.35mm in diameter, so I just need to measure the inside of the rim now and get the rings on order. Thank you very much.
 
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