C70 Rumblin' in Everything but Reverse! Topic is solved

[koolkatkaleb]

So, I've had a Volvo C70 for about three months. 180k miles, transmission reportedly replaced with a used trans last year, just replaced the cat, and struts.

Now here's the deal. When in drive, the car becomes louder. I notice it immediately because I'm familiar with how quiet it was before. It's pretty unnoticeable at idle, but once the RPMs get going you can hear it, even if accelerating in park. If I'm on the highway it quiets down (still noticeable) when the car shifts and the RPMs drop. It's like a nice rumbling sound. You'd think it's the exhaust, but it's not. When in reverse, she's SO quiet. But in drive, from inside the cabin, it sounds like I'm trying to drive a F1 racecar, but again, all of this goes away in reverse, and the car operates as normal until put into park or drive again.

Now again, the car has 180k miles on it. I'm not sure what was put in before, but I changed the oil with 5W-30 full synthetic. I'm not sure if the lighter oil caused the issue, but that's the only thing I can think of that might have had an effect. I just replaced it with high mileage 10w-40, and obviously it didn't solve anything.

I thought it could be the mounts, so I tried engaging the brakes, and reversing, but it sounds good in that instance.

I doubt it's wheel related due to the fact that it sounds fine in reverse, and it sounds much better when cruising in a higher gear.

Fuel pressure, fine. No CEL.

I'm at a loss, and don't want to keep throwing cash down the drain, please help if you have any ideas. I hate driving this car at the moment. Thanks!

[jimmy57]

Get engine and trans mounts checked including the upper torque motion limiter one. The load on those changes forward and reverse.

[koolkatkaleb]

Jimmy,

Still think it could be mounts after my test?

Put the car in reverse, brake so the car remains stationary, and test acceleration. -No issues.
Put car in park/drive, remain stationary. -Rumbling.

[jimmy57]

Yes, the trans is torquing the CV axles two different directions. As a result of this the engine/trans will move opposite the applied torque direction. Raise hood and watch engine for those two tests and you'll see what I mean.

[koolkatkaleb]

Sweet! I had suspected the torque mounts were the issue. I'll check their condition and replace them. I suspect it wasn't done after the trans replacement.

Hopefully the weather fairs well over the next couple of weeks, and I'll sneak in some time to wrench it out.

Thanks Jimmy.

[scot850]

Also check the mount under the crank pulley has not separated. Carefully jack the engine on the RH end under the oil pan. Use a piece of wood to spread the load.

Remove the RH front wheel and then slowly raise the engine and check if the rubber and metal section of the mount has separated.

Neil.

[koolkatkaleb]

Will do Neil. You guys rule and could have saved me hundreds if I started here in the first place!

Ordered the lower/upper torque mounts since I know those need changed. I'll check that lower mount and the remainder during install.

[jenkinskg]

my 04 c70 has a rumble, on mine seems like its the baffles in muffler, hope so.
Just got a new walker online under $200

[koolkatkaleb]

Also check the mount under the crank pulley has not separated. Carefully jack the engine on the RH end under the oil pan. Use a piece of wood to spread the load.

Remove the RH front wheel and then slowly raise the engine and check if the rubber and metal section of the mount has separated.

Neil.

Scot. This was it! Top mount had some deep tears in it, so I know that could use replacement. The bottom torque strut mount was OK, but I went ahead and replaced it. After all that, I still had vibrations. Jacked up the engine to see the RH engine mount fully separate. Nearly all of the rubber had disintegrated. Engine ran fine with the engine jacked! Part will be here Thursday. Finally I can love my Volvo again.

[scot850]

Hopefully it now returns to enjoyable driving! Glad to help.

Neil.