Clunking noise in reverse

[volvoinphill]

Hi everyone, I have been lurking here for awhile and have been able to answer most issues I have had by doing a search. Unfortunately, that is not working for this problem. I have a 2004 XC70 with 108,000 miles. The car runs and drives great but has a problem in reverse. When backing up under moderate acceleration it has some pretty loud clunking noises and shaking. It sounds like it is coming from the front axle area possibly passenger side. I have done all of the usual CV tests and hear nothing while turning, etc. I do know my upper engine mount is torn and the lower rear engine mount may be bad as well. I am going to pick up those parts today. I am wondering if it is possible for the engine to tip so much with the bad mounts that it might cause this clunking/shaking in reverse? Obviously, I will have the answer to that after replacing the mounts but I am wondering if there are any known issues I should be looking for while I have the car on the lift. Any advice would be appreciated. Thank you.

[Astro14]

yep...

you described the conditions where the engine is under max torque and will rotate the farthest in the mounts....R is the lowest gear ratio...

Check ALL the mounts...by 108 K it is likely that they're all shot. Did all 5 (upper, rear, front, passenger side and trans torque mount) about that mileage...and they were all toast.

The front one looked fine...until I took it out and saw that it was cracked all the way through...

Every Volvo I have ever owned went through engine mounts rapidly...something about the stress on them or the design that allows the engine to go under the car in a severe collision I reckon...

[volvoinphill]

Thanks Astro.

It doesn't look like it is the mounts.

I am starting to believe it might be the bevel gear or the coupler. The car has that rusty oil running out of the bevel gear housing and the noise seems to come from that direction.

I am not sure how it would only do it in reverse though, it goes forward perfect.

When it makes the noise it is almost like something is slipping, catching with a clunk and then slipping, catching, etc.

[Astro14]

I am surprised that your mounts all check out (unless you replaced a few and now have elimnated them as a cause...).

I don't personally have experience with the bevel and its failure modes, but your statement, "that rusty oil running out of the bevel gear housing..." worries me.

There are lots of guys who know more on this subject...I recommend surfing the threads...