occasional "clunk" from diff / rear

[ssavill]

Hi,

Wonder if anyone can help / has spotted this in the past... Occasionally, I get what can only be described as a clunk from the rear of the car (i think the diff) slight movement from the back - and then all is fine again.

It is not when the drive train is under stress (i.e. light pull away, or turning around etc)...

Anyone know what it might be - car always seems ok - just occasionally happens.

Thanks all,

Stuart.

[Tokyokev]

Hi Stuart

Have had ths problem since I bought the car. and there are many other postings with similar problem. Do a search for 'Diff Knock' or something to that effect.

The cause of the problem seems to vary from car to car, and you kinda have to go through the motions to find out what yours could be. Here are some clues as to how I fixed mine (still not 100% sorted mind you).

It's important to note that my knock only came when turning a sharp left, and sometime over bumps. It appears to be coming from under the rear seats, also it varied from a low thud to a more hollow sounding clunk, it used to skip or at least appear to skip when turning sharp left as if the diff was sticky.

Try these:

1. Exhaust is rubbing or knocking somewhere,
2. Diff mounts (usually the top mount) replace with more durable poly bushes.
3. ARB mounts (grease them well or replace with poly bushes)
4. Drop links (same as above)
5. Replace your diff oil? Just to be sure.
6. also, there seems to be this weird skip/knock/clunk that happens occassionaly with the hydratrak - you learn to live with it.
7. Check your wheel nuts! Often.... You'd be surprised how loose they get. I check them once a month.

That's all I can think of for now. I am sure others will have some more suggestions. The above fixes haven't solved the clunk 100% - it happens probably once on every 10 drives. So not so bad.

Best

K

Edited by Tokyokev on Saturday 13th January 02:14

[ssavill]

thanks tokoyo - i am getting with the same sort of frequency thatyou are talking about 1 every 10/15 drives - guess i wont worry about it to much :-)

Thanks for the advice

Stuart.

[amazon]

Spooky! Just off going now to get mine checked out for the same thing! I'll post what we find out in case it helps you.

[optimax sniffer]

My 4.5 had this problem, but mainly went turning on/off to the drive & going from forward to reverse. This was cured when the diff bush was replaced.

[budaholic]

Mine developed a similar 'thud' whenever i came off the gas...... it was the top diff bush on mine. Very cheap part, about £18 IIRC, but a pig to get at! apparently.

Bud

[mad mark]

I've got the same thing as well, had it for a year+ now. I had the top diff bush changed but didn't cure it. (currently waiting for a complete set of rear bushes from Clevor Trevor)

But as has been posted above, there are many causes for this 'donk' from the rear.

A thing to check also, is the top diff bush mount. These often break and cant be seen until it is removed. Davetherave had this happen, he posted some pics a while ago.


I did have another rear end knocking that I cured, which turned out to be the roll bar bushes. They stick and therefore cause a knocking as they start to move. I just disconnected the roll bar, an easy job, and the this noise went away so cleaned up the bushes and bar and all is well. (Apart from the other 'donk' from the rear that is).

[BLUETHUNDER]

Its play in the diff.

[amazon]

Update: It seems as though the 'clunk' in my Cerbera has been cured (done 150 miles so far). Provided further miles don't change anything, it appears to have been the Anti Roll Bar - the bushes were fine, but Jules (TCS) greased them and inserted extra spacers and as I said, all seems to be sorted! Thanks Jules!

Edited to add a 'thank you' for the helpful suggestions on this thread too! Sorry - was obviously a bit over excited!

Edited by amazon on Wednesday 7th March 09:24

[Scrooloose]

I was going to post about this.

I seem to have a similar problem, although it also manifests as a juddering when holding the car at a constant speed, say about 30mph in 3rd...

When completely off the throttle it's fine, likewise when accelerating gently.

I thought that it could be the diff. Anyone care to elaborate?

[whatever]

Scrooloose said:

I was going to post about this.

I seem to have a similar problem, although it also manifests as a juddering when holding the car at a constant speed, say about 30mph in 3rd...

When completely off the throttle it's fine, likewise when accelerating gently.

I thought that it could be the diff. Anyone care to elaborate?

Not entirely sure if this is what you're describing, but if you're holding a steady speed on a very light throttle (i.e. literally not much more than just resting your foot on it) then you can get a "jiggly" sort of response from the engine, which in the past I have had diagnosed (and fixed) as a dodgy throttle pot not giving the correct reading, putting (aiui) the two banks somewhat our of balance.

Coming off the gas fixes it (as there's no throttle being applied) and pressing down a bit further (to accelerate gently (or even harder)) fixes it, as the difference between the two banks is proportionally less.

Also: dependnig on when it was last services / set up the balance between the two banks may be off anyway.

[Scrooloose]

whatever said:

Scrooloose said:

I was going to post about this.

I seem to have a similar problem, although it also manifests as a juddering when holding the car at a constant speed, say about 30mph in 3rd...

When completely off the throttle it's fine, likewise when accelerating gently.

I thought that it could be the diff. Anyone care to elaborate?

Not entirely sure if this is what you're describing, but if you're holding a steady speed on a very light throttle (i.e. literally not much more than just resting your foot on it) then you can get a "jiggly" sort of response from the engine, which in the past I have had diagnosed (and fixed) as a dodgy throttle pot not giving the correct reading, putting (aiui) the two banks somewhat our of balance.

Coming off the gas fixes it (as there's no throttle being applied) and pressing down a bit further (to accelerate gently (or even harder)) fixes it, as the difference between the two banks is proportionally less.

Also: dependnig on when it was last services / set up the balance between the two banks may be off anyway.

Thanks - i'll check it out. Although the engine note/revs do seem to be completely constant whilst the problem happens.....

[StefT]

I had a similar problem last year. The clunk varied from a slight knock to an almighty thump at times mainly when the car was turning slowly to either side and the car always creaked and groaned when pulling away. I thought mine was going to be a diff problem but it turned out to be a busted drop link. They were both replaced by PPC in Melton and the car has been transformed since then, lovely smooth drive and all the noises have gone.