V70 Drivetrain Thump?

[barrybritcher]

next time I order some driveshaft bolts I'm going to measure the before and after length.

I'm sure these are good for a few loosen / tighten cycles

[Tentontimmy]

Originally Posted by Clan

well that knock is what you are hearing i would say .. what is it ? That's the question ...
no the top torque reaction bar is fine thats how it is , it doesn't rotate in normal use it just takes the back and forward thrust front the engine .

Thanks for the input.

Apologies for the confusion: what I am trying to diagnose in these videos is a thump/jolt sensation when lifting off and applying the throttle. It’s something you can feel rather than hear.

I appreciate there is a clunking noise in one of the videos but that is just a coincidence I believe. I think that is a loose drive shaft bolt. It was supposed to have been sorted by my mechanic the other day but it has come back. To fix it properly I suspect I will need to try new bolts.

Back to the thump/jolt sensation, I am inclined to try some inserts to stiffen the strut brace, and see if that helps. I note what you say about the brace being to help with the back and forth movement of the engine, and that ties in with what I am feeling. It’s as though the engine rocks back and forth while loading and unloading, coming to an abrupt stop at each end of its travel. I am wondering if a slightly stiffer brace will help cushion the abrupt stop and smooth out the thumping sensation.

Thanks again for the input so far.

[Clan]

Originally Posted by Tentontimmy

Thanks for the input.

Apologies for the confusion: what I am trying to diagnose in these videos is a thump/jolt sensation when lifting off and applying the throttle. It’s something you can feel rather than hear.

I appreciate there is a clunking noise in one of the videos but that is just a coincidence I believe. I think that is a loose drive shaft bolt. It was supposed to have been sorted by my mechanic the other day but it has come back. To fix it properly I suspect I will need to try new bolts.

Back to the thump/jolt sensation, I am inclined to try some inserts to stiffen the strut brace, and see if that helps. I note what you say about the brace being to help with the back and forth movement of the engine, and that ties in with what I am feeling. It’s as though the engine rocks back and forth while loading and unloading, coming to an abrupt stop at each end of its travel. I am wondering if a slightly stiffer brace will help cushion the abrupt stop and smooth out the thumping sensation.

Thanks again for the input so far.

You need to properly diagnose your problem , The standard parts are entirely adequate and give no jolt whatsoever .. Its difficult to help without being there ... there is something wrong with the engine mounts or top or bottom Torque reaction rod bushes . Maybe a suspension component as a last resort ... It would help if you could reproduce it on a 4 post lift whilst someone watches from underneath . Or just give it to a volvo dealer to sort out :-)

[BarryCambs]

Have you checked the inboard cv joint for play?

[Simmy]

Originally Posted by Tentontimmy

Thanks for the response. Yes I did used to hear a click/clunk sound under the circumstances you describe. It seems to have gone away now the axle bolt has been tightened though.

The drivetrain thump is more of a jolt/thump sensation, rather than something that can be heard. I will keep digging into it.

also worth checking are the wish bone bushes and cv joints and subframe bushes

[Bashy]

Originally Posted by Tentontimmy

Back to the thump/jolt sensation, I am inclined to try some inserts to stiffen the strut brace, and see if that helps. I note what you say about the brace being to help with the back and forth movement of the engine, and that ties in with what I am feeling. It’s as though the engine rocks back and forth while loading and unloading, coming to an abrupt stop at each end of its travel. I am wondering if a slightly stiffer brace will help cushion the abrupt stop and smooth out the thumping sensation.

Thanks again for the input so far.

I always thought the strut brace was to stiffen the 2 front struts, reduce left-right-right left movement hence why there is a lot of play when you twist or move back and forth, try moving it sideways

[barrybritcher]

Have you looked at the engine mount behind the access panel in the drivers wheel well. Next to the timing belt / vibration dampener / crank pulley

[Clan]

Originally Posted by Bashy

I always thought the strut brace was to stiffen the 2 front struts, reduce left-right-right left movement hence why there is a lot of play when you twist or move back and forth, try moving it sideways

No it's not a strut brace, a volvo chassis does not flex around like a Mk 3 Escort does , you can bent the strut towers in and out by hand on those !

The black beam is purely a stay to take the torque reaction of the engine when its under load .

[Bashy]

Iworking on mine now and yeah, I see what you mean, it's not actually on the struts like the one I had on the C70...

[Tentontimmy]

Originally Posted by Clan

You need to properly diagnose your problem , The standard parts are entirely adequate and give no jolt whatsoever .. Its difficult to help without being there ... there is something wrong with the engine mounts or top or bottom Torque reaction rod bushes . Maybe a suspension component as a last resort ... It would help if you could reproduce it on a 4 post lift whilst someone watches from underneath . Or just give it to a volvo dealer to sort out :-)

LOL, thanks I will keep digging into it. Top and bottom torque reaction rods/mounts have been changed to no effect, but one of the other things you mention will hopefully be the culprit.