Clunking Differential - play/ backlash?

[charlh94]

I obtained a Cabrio over the lockdown which I’ve just got on the road for the first time in its life. Just joined the owners club and hence this is my first post.

Along with a list of other areas that needs work, I’ve got an issue with the diff which I could do with some advise on pretty please...

When stationary, going into drive and reverse there’s a clunk (could be the bw65, but keep reading).
When driving, going off and on the power, there’s a clunk.
If holding a speed, there’s a rough noise- which I gather is powertrain taking up the slack off and on constantly if that makes sense.
Also I sometimes hear a kind of binding noise when coming near to a stop (sounds like rusty brakes, but it isn’t).

So sure enough, I crawl underneath and there’s what seems to be a lot of play in the prop shaft... when in park there’s no movement. In neutral I can rotate it a fair amount- see video:

https://drive.google.com/file/d/1TkMeWStjUDcl4Rtbae-sh-TScZTexS2a/view?usp=drivesdk

You can see in that video that there’s not a lot of movement in the UJ.
I then put one wheel up in the air at a time and tried to see if there’s any movement in the UJs within the drive shaft rubber boots, but seems like there’s not.
I took another video to try and show the relationship between me turning the wheel and the prop shaft, but it’s not very clear, here it is anyway:

https://drive.google.com/file/d/1TkMeWStjUDcl4Rtbae-sh-TScZTexS2a/view?usp=drivesdk

So I’m guessing the backlash is completely out/ issue with pinion bearing and preload. But I have next to no experience with diffs so if anyone could offer some advise on what to do next or who to talk to it would be much appreciated.

[milliemarlin]

Re: Clunking Differential - play/ backlash?

Hi, and welcome to the club.

Assuming your diff is from a Ford Sierra, the first clunk think I think of is the rear diff mounting. That is an encased rubber affair and after all these years many have perished. This results in a clunk when power or engine braking causes the unit to swing to either side. There is not much room for movement in the car. You may be able to see marks where the diff has touched the sides. You should especially check that the diff is not hitting the fuel tank as that is never a good thing.

The good news is that although originals are not available; some companies make alternatives, at a price. The bad news is there is a lot of disassembly required to get at it.

Paul

PS: It would be great to see a picture of the car and our archivist would be delighted if you could give him details of the car reg and chassis number etc if you haven’t already given him them.

[charlh94]

Re: Clunking Differential - play/ backlash?

Hi Paul, there is a bit of movement on the diff as it comes on or off power, but I couldn’t see evidence of it hitting anything and definitely not the fuel tank. I’ll have a another look to confirm this though thanks.
Just rotating the shaft with my hand like in the video I can replicate a small clunk so I’m pretty sure the noise is from within.

And yes I will send some photos in soon

[milliemarlin]

Re: Clunking Differential - play/ backlash?

Hi Charlh94,
I would still guess that something is not as secure as it should be. You have ruled out a clunk inside the diff as there is little backlash. Ford diffs are very robust. When worn make more of a steel on steel whine under load than a clunk. Other mountings such as engine or gearbox can clunk. You should also check the trailing arms and anything on the rear axle assembly. I have had drum brakes clunk when improperly mounted. At this distance it is hard not to just state the obvious.

You say it is it’s first time on the road I am sure we would all be interested to see any build pictures you have, as well as the final car. The history of your car and the story of how you passed IVA is always fascinating to me and other members. Perhaps a retrospective build diary on this web site or an article for PitStop.
Paul

[greyV8pete]

Re: Clunking Differential - play/ backlash?

I obtained a Cabrio over the lockdown which I’ve just got on the road for the first time in its life. Just joined the owners club and hence this is my first post.

Along with a list of other areas that needs work, I’ve got an issue with the diff which I could do with some advise on pretty please...

When stationary, going into drive and reverse there’s a clunk (could be the bw65, but keep reading).
When driving, going off and on the power, there’s a clunk.
If holding a speed, there’s a rough noise- which I gather is powertrain taking up the slack off and on constantly if that makes sense.
Also I sometimes hear a kind of binding noise when coming near to a stop (sounds like rusty brakes, but it isn’t).

So sure enough, I crawl underneath and there’s what seems to be a lot of play in the prop shaft... when in park there’s no movement. In neutral I can rotate it a fair amount- see video:

https://drive.google.com/file/d/1TkMeWStjUDcl4Rtbae-sh-TScZTexS2a/view?usp=drivesdk

You can see in that video that there’s not a lot of movement in the UJ.
I then put one wheel up in the air at a time and tried to see if there’s any movement in the UJs within the drive shaft rubber boots, but seems like there’s not.
I took another video to try and show the relationship between me turning the wheel and the prop shaft, but it’s not very clear, here it is anyway:

https://drive.google.com/file/d/1TkMeWStjUDcl4Rtbae-sh-TScZTexS2a/view?usp=drivesdk

So I’m guessing the backlash is completely out/ issue with pinion bearing and preload. But I have next to no experience with diffs so if anyone could offer some advise on what to do next or who to talk to it would be much appreciated.

That movement of the propshaft does seem excessive. With the movement and noise in your videos I would suspect wear or bearing failure in the diff internals. That clonk sounds a bit “dry” to me. The oil level may have been neglected which could be the cause of any wear or failure. The rough noise when driving would also point to excessive diff internal wear.


Also best to check for play in the drive shaft and prop shaft joints to eliminate those.


If you can jack one rear wheel on an axle stand with the other three wheels chocked and the handbrake off, without the engine running, put the car in top gear and get someone to turn the wheel to and fro. That should help you to pinpoint the source of the clonk. Also check how far the wheel can rotate to and fro. If it is excessive it would point to the diff being the problem. Peter.

[dcunn]

Re: Clunking Differential - play/ backlash?

I agree with Peter, my Hunter had an annoying clunk, with movement similar to yours apparently "within" the diff.

A less worn diff cured the problem

If you look to source another, be aware that there are a myriad of different ratios

[dogoncrazy]

Re: Clunking Differential - play/ backlash?

Might seem like a daft question but has it got oil in it? Don't assume anything - CHECK

[charlh94]

Re: Clunking Differential - play/ backlash?

Hi Charlh94,
I would still guess that something is not as secure as it should be. You have ruled out a clunk inside the diff as there is little backlash. Ford diffs are very robust. When worn make more of a steel on steel whine under load than a clunk. Other mountings such as engine or gearbox can clunk. You should also check the trailing arms and anything on the rear axle assembly. I have had drum brakes clunk when improperly mounted. At this distance it is hard not to just state the obvious.

You say it is it’s first time on the road I am sure we would all be interested to see any build pictures you have, as well as the final car. The history of your car and the story of how you passed IVA is always fascinating to me and other members. Perhaps a retrospective build diary on this web site or an article for PitStop.
Paul

I thought I’d shown that there is a lot of backlash?
I’ll have a better look at the diff mounting, but I think the only movement is from the D bracket rubber.

Also where would be the best place to put some info about the car other than pitstop?

[charlh94]

Re: Clunking Differential - play/ backlash?

That movement of the propshaft does seem excessive. With the movement and noise in your videos I would suspect wear or bearing failure in the diff internals. That clonk sounds a bit “dry” to me. The oil level may have been neglected which could be the cause of any wear or failure. The rough noise when driving would also point to excessive diff internal wear.


Also best to check for play in the drive shaft and prop shaft joints to eliminate those.


If you can jack one rear wheel on an axle stand with the other three wheels chocked and the handbrake off, without the engine running, put the car in top gear and get someone to turn the wheel to and fro. That should help you to pinpoint the source of the clonk. Also check how far the wheel can rotate to and fro. If it is excessive it would point to the diff being the problem. Peter.

If this damage is the cause, what’s the best course of action?

Ah yes I did lift one wheel at a time and turn, but did it in neutral, I’ll try again in park (it’s an auto) and see how much play there is and pinpoint It a bit better like you say.

[charlh94]

Re: Clunking Differential - play/ backlash?

I was really hoping not to have to change it, but we will see!

[charlh94]

Re: Clunking Differential - play/ backlash?

Might seem like a daft question but has it got oil in it? Don't assume anything - CHECK

Now you’ve said this I’m definitely going to be checking haha! Do I just take out the fill plug and stick something in to see if the level is just below the plug?
If this is the case, will a refill likely solve the clunking? Or is it too late if the noise is there? (The cars only done a few hundred miles, but I have no idea on the history of the diff).

[greyV8pete]

Re: Clunking Differential - play/ backlash?

Do all the checks to eliminate other causes and then accept that the diff has probably had it! Adding oil now if its empty won’t fix the damage. The filler plug is difficult to reach on the Cabrio as the fuel tank is in the way. Probably why it doesn’t get checked! I cut the end off an allen key to leave just enough sticking out to fit a flat ratchet type combination ring spanner on the end.


To remove the diff you need to jack the rear of the car onto axle stands under the rear of the chassis. Then you can undo the rear brakes and pull out the drive shafts. Get hold of a Haynes Sierra workshop manual as it tells you how to do all this. THE DIFF IS HEAVY! I made up a jack to swap mine! There is a post on this forum showing how I replaced my rear diff mounting which may help you. Once the diff is out of the car you can remove the rear cover plate and check for damage. Rebuilding one is not a diy job! Best source a used one in good condition. I obtained mine (replaced for ratio change) from John at Kitfit. I have his phone number if you need it.


The diff ratio will be stamped on the edge of the crownwheel. The following link is invaluable for identifying Sierra diff types / sizes and ratios. Peter.


http://www.super7thheaven.co.uk/comp..._differential/

[dcunn]

Re: Clunking Differential - play/ backlash?

Mornin' charlh94

If you're really lucky, there may be a tag on the back of the diff to tell you it's ratio - like this one !

Please send details/pics of the car to my email as in Pitstop magazine

Rgds Dave Cunnington Archivist

[dogoncrazy]

Re: Clunking Differential - play/ backlash?

I was aware of the backlash as seen in the video. My suggestion of checking the oil was on the premise of if none is present then you really don't need to look any further as the unit is probably beyond redemption.
I know of one member who having installed a reconditioned axle in his Roadster had it blow itself to pieces on the A38 out of Derby. He either assumed it had been filled with oil or just forgot to make the check. An expensive oversight !

[charlh94]

Re: Clunking Differential - play/ backlash?

Update: Had a look today and the oil is low!

Looking for a source of a leak I found the rubber boots around the cv joints are full of oil (should just be grease, right?) and there are a couple of tears where it can seep out.

The paperwork I have shows the diff oil was done in 2016 which was only a couple of hundred miles ago.

I’ve ordered a Sierra Haynes.

Does anyone think if I replace the seals going to the cv joint (not sure how feasible that is), then I might just be lucky enough to not have to source a new diff?