Thwauk in front left of car, is it the CV axle?

[gibbons]

Our 04 XC70 has 155,000 miles. In the last 6 months it's developed a "thwauk" thump sound when I drive over the slightest of bumps, at about any speed, even driving in the driveway approach. It does it going straight, turning, accelerating, at cruise, and decelerating. I can't find any maneuver that mutes it. It never clicks on turns or otherwise.

I thought it might be a motor mount, but the top mount looks good. The one on by the passenger wheel was replaced at 100K just for fun. Can't tell about the big one in front. But if I rock the car back and forth on the driveline backlash in park, I think this is the thwauk sound driving, it sure sounds like it's by the front driver's side lower drivetrain area. I've yanked and tugged on all the suspension parts, nothing seems loose. I replaced the lower A-arms with the struts at 85K. Here is the driveline backlash, anyone familiar with how much theirs has? https://www.youtube.com/watch?v=DMDSJhoWd-A

The CV boots haven't leaked, but I am wondering about them. Here is a video of my tugging showing linear play, lifting showing radial play, and slop in the spline shaft where it enters the transmission. As I never monkey with this stuff, I'm wondering if it's normal? https://www.youtube.com/watch?v=2GYcECnbxk8

I've done bearings twice in the front, and struts. To put in a CV axle, do you just remove that bolt from the hub, knock the knuckle out of the A-arm, pull it aside, pull the axle out of the bearing, and tug the whole assembly out of the trans? Reverse order to install? As I recall, there can be issues with the snap ring around the splined shaft that makes it hard to put a new one in?

Ugh...

[billr99]

Back to the basics. Could it be endlinks? I have found that even when worn they won't display wear, even when tugged on, if they are under any kind of load (like droop if the car is in the air).

Good Luck,

Bill

[Astro14]

OK - the outer joint in your axle is a CV joint: balls in a race that allow constant angle changes. The inner joint is a tripod joint, it allows the axle to move in/out. The axle has to move in/out or your suspension couldn't go up/down.

Now, the in/out play: normal.

The rotational play in the tripod joint: not normal/worn.

The rotational play in your transmission: wear, but not fixable

The movement of your engine: not normal.

Your axle has excess wear. You engine mounts need replacing. There are 5. You checked one of them. They last 60-80K miles. Start with replacing all the motor mounts. They need it anyway. Don't use cheap mounts. Use Volvo OEM or Lemforder. Hutchinson should be OK, to.

Once you've got the mounts done (rear one is a PITA), see where you are. If the "thwack" is still there, then consider the axle. Axle is easy, it's as you describe, but getting out of the case is hard. The axle popping tools that I have would not work. I ended up with the dealer doing it - the mechanic used a big cold chisel between the case and axle and "popped" it out with a single hard blow from a large hammer.

[gibbons]

Doh! I had my brain in neutral on the CV axles, simultaneously stressing brake caliper pistons that won't retract on my mountain bike, my son's Sube's head gaskets, low pressure in my lawn sprinkler system... I've replaced axles on Sube's and Hondas in the past. I know the routine, don't yank the outside, or you will pull the inner linear joint apart...

OK, I will do the motor mounts. I see a replacement kit from FCP.



FCP also has Hutchinson for about half the price. Don't do it? I don't care that much about the cost, the bicycle brakes are going to $500...

Thanks for the help!!!

[Astro14]

Hutchinson didn't last for me...and that rear engine mount is such a pain on this car that I really wouldn't want to do it very often.

The lower torque mount fails quickly, no matter what you use. I ended up cobbling together a couple of polyurethane bushings, using IPD and other brand parts, for that lower torque mount and I'm much happier. The poly upper engine mount is simply awful - way too much vibration and harshness transmitted into the cabin.

I didn't realize who was posting, I just responded, and I apologize if I came across overly simple for a guy with your experience. The question seemed basic, and I answered presuming that I would have to fill in the gaps in your knowledge....but I realize now that I could've done without the explanation...

Cheers,
Astro

[Leto Atreides II]

FCP says Hutchinson is the OE manufacturer anyway -- should be the same part as Volvo without the Volvo sticker. Is that not the case?

[gibbons]

Thanks Astro! No, you weren't overly simple. My question was. Thanks for acknowledging it.

A complete set of Volvo OEM motor mounts is on the way from FCP. Along with enough oil filters to last me into the next decade. This car and I are buddies, I will keep it running. And the styling was so odd, and there were so few, that people don't know I'm driving a car that's this old!

I saw a youtube about that rear pad mount... can't wait...

[gibbons]

OK, I replaced all the mounts a year ago and it didn't make any difference. Rats! So for a year I have been annoyed by the clunk. A I work with said, "it's your sway bar end links". Like billr99 said in the first reply. So I bought a set of Moog units for $50, I was going to try anything at this point. I first three ball joints I un-nutted seemed tight, and I was discouraged. Then the fourth one... play! The tiniest amount, maybe .020". But with the new Moogs on, the clunk went away. Yay!!!

So I though that was a fun $50. I think I'll do the rears just for giggles. So I got another set, and they fixed my rear hatch clunk I've been putting up with for years, even moving the striker so tight it's hard to close the hatch. Yeah, one out of four balls had a tiny bit of play.

So for $100, I feel like I got a new car. Except for the driveline clunk that I think is associated with a top motor mount.

And as far as installation, it was easy. My impact driver spun all the nuts off. After they loosened, the ball would spin, but the high RPM of the impactor beat the ball. They were hot when they came off

[Pennhaven]

OK, I replaced all the mounts a year ago and it didn't make any difference. Rats! So for a year I have been annoyed by the clunk. A I work with said, "it's your sway bar end links". Like billr99 said in the first reply. So I bought a set of Moog units for $50, I was going to try anything at this point. I first three ball joints I un-nutted seemed tight, and I was discouraged. Then the fourth one... play! The tiniest amount, maybe .020". But with the new Moogs on, the clunk went away. Yay!!!

So I though that was a fun $50. I think I'll do the rears just for giggles. So I got another set, and they fixed my rear hatch clunk I've been putting up with for years, even moving the striker so tight it's hard to close the hatch. Yeah, one out of four balls had a tiny bit of play.

So for $100, I feel like I got a new car. Except for the driveline clunk that I think is associated with a top motor mount.

And as far as installation, it was easy. My impact driver spun all the nuts off. After they loosened, the ball would spin, but the high RPM of the impactor beat the ball. They were hot when they came off

Always a good feeling when you sort out one (or two!) of these headaches! The Moog links are the best I've had.