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Knocking/Clunking noise over bumps

I recently did a diff & transmission oil change, and straight after that I took the car for a test drive. Straight away I noticed a knocking/clunking sound coming from the rear middle of the car when going over speed bumps or any rough road surface. This happens regardless of the speed when going over bumps and is really irritating. I never used to get this problem before and the car drives like a dream, apart from this 1 issue now.

Is there anything in particular I should check?

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Reply 1

Braveheart2009

I had the same problem it was the anti roll bar link you can get them cheap but remember to tell the mechanic to shake your suspension to see which one it is as my previous mechanic installed 2 and didn't sort the problem as it was the front driver side one!

Bushes, probs.

Could be many things.

Failed exhaust mount,
Loose suspension mount
Goosed suspension bush
buggered damper
Loose heat shield
Spare wheel / tools loose in the boot

Get under there and start looking.

Reply 4

RB59

It's not exactly quiet either. I can hear it with the stereo on level 20 which is loud enough that you can't hear the person next to you speak. I've experienced squeaks before but this is nothing like it. It's definitely a clunking sound. But thanks I will check these tomorrow when visibility is better. Cheers. any other ideas?

Reply 5

gbduo

Well I can't imagine it is co-incidence that you did an oil change and straight after the noise started.

Do you think anything could have fell into the Diff? And did you use the right oil? What did you have to remove to change the oil in the diff?

Reply 6

shark67

I bet its the shock absorber

Reply 7

RB59

gbduo

Nothing would have fell into the diff. Well I did use a hand pump to pump the new oil into it but that had no loose parts and i'm sure nothing fell into it except the new oil. For the record I used REDLINE Synthetic Gear Oil 75W-90 GL5 in the diff. It meets manufacturer specifications and loads of other people have used it with good success.

Only removed the fill and drain plugs and replaced them later with new washers.

Reply 8

gbduo

RB59

Yeh, that sounds about right, just checking you did not make a silly DIY mistake and put in 5w30! Don't take it wrong/personally, just always good to discount the obvious first.

So you did not loosen anything around the diff other than the sump plug to empty/refill the diff?

Reply 9

JC.

Even if it was the wrong oil in the diff, it would whine rather than nock.

OP, can you re-create the issue by bouncing the car on the suspension?

Reply 10

gbduo

Oh just saw your edit. Looks like I am barking up the wrong tree then with the diff!

Very odd for something to fail which is irrelevent to something just fixed, from experience, it is usually the thing you thought you had fixed which then has more problems than when you started! You actually have a full blown, co-incidental problem here then!

When does the noise happen, is it constant? Does it occur on bumpy roads? Under braking? Under acceleration? Is it rhythmical?

Reply 11

gbduo

JC.

Even if it was the wrong oil in the diff, it would whine rather than nock.

OP, can you re-create the issue by bouncing the car on the suspension?

Fair shout.

Reply 12

RB59

JC.

OP, can you re-create the issue by bouncing the car on the suspension?

Tried the bouncing trick on both sides and I can't re-create the noise :frown:

gbduo

When does the noise happen, is it constant? Does it occur on bumpy roads? Under braking? Under acceleration? Is it rhythmical?

Yes it's constant, over every speed bump or rough surface I always get the same sound. Even when cornering moderately hard over bumpy roads (Not a good idea, I know) I get the same sound. No difference regardless of speed, acceleration or deceleration. I will see if I can record a sound bite as it's fairly loud and easy to hear. Let me say one more time the car does still drive perfect with no loss in performance or anything.

Reply 13

gbduo

I think it could be a knackered bearing then or a CV joint that has gone. I definitely think it is transmission related and not the suspension.

Reply 14

CurlyBen

gbduo

Yeh, that sounds about right, just checking you did not make a silly DIY mistake and put in 5w30! Don't take it wrong/personally, just always good to discount the obvious first.

To be fair, 75w90 gear and 10w40 engine oils are similar viscosities, they're just measured differently. There are some other differences between them but viscosity isn't normally the issue.

Is it a Ford KA?

Speed bumps + knocking = Wheel bearing for me.

Reply 17

JC.

magnificentduke

Speed bumps + knocking = Wheel bearing for me.

No. If it were a wheelbearing it would be apparent at all roadspeeds no matter the level of the road surface.

Reply 18

Nick Longjohnson

I once had a focus that did that. Horrible suspension bushings on the old ones

Reply 19

magnificentduke

JC.

No. If it were a wheelbearing it would be apparent at all roadspeeds no matter the level of the road surface.

He said it is apparent at all road speeds.... And there is no doubt that you notice ****** bearings much better when you hit something than when you're just driving along.

I'm not saying I'm right btw, just something to look at.