V70 Drivetrain Thump?

[Clan]

Originally Posted by Tentontimmy

Update: the clunking sound was indeed a loose axle bolt - thanks Georgeandkira.

The drivetrain thump persists however, further investigation is needed.

you must have a new bolt correctly torqued and angle tightened as they are use once stretch bolts ... it would be a good idea now to trickle some locktite along the splines from the outer end of the shaft just to take up any play due to the prolonged shunting back and forth .

[Tentontimmy]

Originally Posted by Clan

you must have a new bolt correctly torqued and angle tightened as they are use once stretch bolts ... it would be a good idea now to trickle some locktite along the splines from the outer end of the shaft just to take up any play due to the prolonged shunting back and forth .

Thank you, that makes sense. I wonder if eliminating the play you mention will help get rid of the drivetrain thump I am experiencing.

[Clan]

Originally Posted by Tentontimmy

Thank you, that makes sense. I wonder if eliminating the play you mention will help get rid of the drivetrain thump I am experiencing.

If it a solid clunk every time the torque reverses direction under power application then yes most likely ...

[Tentontimmy]

Originally Posted by Clan

If it a solid clunk every time the torque reverses direction under power application then yes most likely ...

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.

[Clan]

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.

Ahh so you have two problems ... what happens if you disconnect the top engine torque reaction rod and try rocking the engine back and forth with it in gear ?

[Kev0607]

Could it be your transmission mount by any chance? Have a look underneath the car around the gearbox area & you'll see the part I'm referring to (It looks a bit like a ratchet strap). Try wiggling it by hand, it should be pretty solid. If there's free play & you can move it by hand, then chances are, this could be your culprit causing the clunk.

[Tentontimmy]

Originally Posted by Clan

Ahh so you have two problems ... what happens if you disconnect the top engine torque reaction rod and try rocking the engine back and forth with it in gear ?

Thanks, yes two problems unfortunately. I will try that and see what happens. I have replaced both top and bottom engine mounts/torque control arms and the problem persist, but perhaps one of the other engine mounts or subframe bushings is bad. I wouldn't be surprised after 233k miles!

[Tentontimmy]

Originally Posted by Kev0607

Could it be your transmission mount by any chance? Have a look underneath the car around the gearbox area & you'll see the part I'm referring to (It looks a bit like a ratchet strap). Try wiggling it by hand, it should be pretty solid. If there's free play & you can move it by hand, then chances are, this could be your culprit causing the clunk.

Hi Kev, thanks yes I too thought that lower mount might be the culprit. I changed it for a new one (together with the top engine mount) but sadly the thump is still there. I need to keep digging.

[Tentontimmy]

Originally Posted by Clan

Ahh so you have two problems ... what happens if you disconnect the top engine torque reaction rod and try rocking the engine back and forth with it in gear ?

OK, we could be getting somewhere.

Here is a video showing what happens when I rock the car back and forth with the car in gear and the top engine torque reaction rod bolt removed: https://www.youtube.com/watch?v=F8Qf-09f8j0

Any thoughts on whether this movement looks abnormal?

Leaving that aside, I noticed that the strut brace has lots of play in it. The brace rocks back and forth with barely any effort. See this video: https://www.youtube.com/watch?v=74GG6f1phEQ

That much play in the brace can't be normal, can it? And since the top engine mount connects directly to the brace, that could very well be the source of the thump I am feeling. Time for replacement strut brace bushes?

Any thoughts gratefully received!

[Clan]

Originally Posted by Tentontimmy

OK, we could be getting somewhere.

Here is a video showing what happens when I rock the car back and forth with the car in gear and the top engine torque reaction rod bolt removed: https://www.youtube.com/watch?v=F8Qf-09f8j0

Any thoughts on whether this movement looks abnormal?

Leaving that aside, I noticed that the strut brace has lots of play in it. The brace rocks back and forth with barely any effort. See this video: https://www.youtube.com/watch?v=74GG6f1phEQ

That much play in the brace can't be normal, can it? And since the top engine mount connects directly to the brace, that could very well be the source of the thump I am feeling. Time for replacement strut brace bushes?

Any thoughts gratefully received!

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 .