woo woo sound between 2100 and 2300 RPM on acceleration

Goosey · Post by **Goosey** » 30 Oct 2018, 17:29

My 99 XC with 391120 Km on it runs like a charm. I've put a used transmission in it because reverse went and replaced the turbo but it still runs well. Over the last few months it's developed an interesting gurrring sound when accelerating and then goes to wooo wooo between 2100 and 2300 rpm. It doesn't do any of this while just running and there is no vibration to go along with it. I've replaced all of the motor mounts so it's nothing vibrating on the frame as far as I can see. I did replace the torque mounts with IPD poly ones but it was making the sound before that. I was wondering if it's the angle gear or the coupler between the angle gear and the trans or possibly the drivers side drive shaft has gotten loose but I would think it would vibrate if that was the case. Any Ideas????

Post by **wizechatmgr** » 30 Oct 2018, 17:49

Happen to check the bearing where the drive shaft goes into the torque coupler/conditional disconnect (can't remember Volvo name...) approximately under the passenger's seat?

Goosey · Post by **Goosey** » 30 Oct 2018, 18:21

Not sure what you mean. The bearing on the angle gear where the drive shaft to the rear wheels connects seems to be fine. The noise seems to be ahead of the firewall and a little to the left but it's hard to tell.

Post by **wizechatmgr** » 30 Oct 2018, 18:43

Ah, yeah, totally different area than I was thinking... Reading doesn't appear to be my strong point tonight.

WhatAmIDoing · Post by **WhatAmIDoing** » 31 Oct 2018, 09:31

To me, the described noise and location makes me think turbo. Boost leak, exhaust leak maybe?

dj_v70 · Post by **dj_v70** » 31 Oct 2018, 11:03

I think the part that wizechatmgr was suggesting is the driveshaft carrier bearing for awd. I don't have awd, but my old 240 rwds had issues with these. They start to go around 200kmi and make a similar noise. My understanding is that the s70/v70 awd had this issue, it is usually worse when cold upside and when just starting to drive it. The location doesn't seem to fit exactly where you are suggesting but these noises are hard to pinpoint sometimes so it is worth considering.

You stated that "It doesn't do any of this while just running and there is no vibration to go along with it." Please define running. Do you mean that if you rev the engine while in park that it doesn't make this noise?

Is this purely rpm dependent or does it happen in all gears?

When you hear the noise, did you try to put the car in neutral (I also turn engine off, but only consider that if you fully understand the safety implications!) and see if the noise goes away? This separates engine noises from other potential suspects and could remove turbo as possible culprit.

Goosey · Post by **Goosey** » 31 Oct 2018, 11:13

In park revving the engine it doesn't make the noise. Just when accelerating in drive. Also I removed the driveshaft to the rear wheels thinking it might be one of these components and there was no change so I put if back in. The sound is almost like a vibration buzz that oscillates at a certain RPM. The most frustrating thing is that it isn't consistent. I checked the isolation mount for the upper torque mount at the firewall and that seemed to be fine.

I am thinking that it might have something to do with the turbo since I did the swap and I'm not the most consistent mechanic with replacing things like gaskets so it might be a gasket leak at the turbo. But of course my question is still why isn't it consistent.

Goosey · Post by **Goosey** » 31 Oct 2018, 11:14

I'm new to this forum so I want to thank everyone for your input

Goosey · Post by **Goosey** » 31 Oct 2018, 11:16

Just another thought. If it was a turbo leak you'd think it would happen even when it's not in gear.

dj_v70 · Post by **dj_v70** » 31 Oct 2018, 13:31

Goosey wrote: ↑31 Oct 2018, 11:16 Just another thought. If it was a turbo leak you'd think it would happen even when it's not in gear.

Not necessarily, it could require rpm and load. That is why I am asking if it happens in all gears at those rpms. If it does, it is engine related. If not it is drivetrain related (which could be for front wheels or back).