IRS Rear End Clonking Possibilities

[RogerH]

IRS Rear End Clonk

 

Wire wheel loose on splines

Wire wheel adaptor nuts loose

Steel wheel nuts loose

Something in the boot

Lever arm damper attachment bolts loose

Lever arm drop link loose

One or more of the 4 diff support pins broken on the chassis

Drive shaft splines worn

Drive shaft UJ’s worn

Drive shaft/diff attachment bolts loose

Driveshaft spline lock

Propshaft splines worn

Propshaft UJ’s worn

Propshaft attachment bolts lose

Diff input pinion loose/to much play

Diff output half shaft key worn

Diif front brace attachment bolts

Diff pin loose nuts

Exhaust system knocking

TRailing Arm bushes

TRailing Arm brackets cracked/loose

TRailing Arm attachment bolts loose

Trailing Arm chassis member cracked

Doors clunking on the anti-burst brackets

Body loose on the chassis

Edited July 28, 2018 by RogerH

[Z320]

Tool left anywhere on the car after work

[Drewmotty]

Diff front mounting bracket cracked.

[REJones]

Thanks Roger for your rather frightening list of potential culprits. Going through it may take a bit of time.

 

Richard

[Z320]

New hubs with central nut not tight enough

[tonycharente]

Excellent list, Roger !

I had my diff rebuilt following two broken pinion teeth, and I have since replaced both drive shafts, but I still have a clonking noise on acceleration / lift off / acceleration (TR4A IRS).  I'm having a hard time trying to tell where it is coming from.

Of course I fear the dreaded right-front differential  mount stud syndrom most, although all the diff mount studs seemed solid enough when I had the rear axle out for its rebuild.  This is the one thing I fear the most  -  I can live with anything else...

I came across an article in an American magazine ("Classic Motorsports, July 2017") that read as follows:-

"With the engine running and your foot very firmly on the brake, slowly release the clutch while using the brake to hold the car in place. [It doesn't say so, but I presume this is with first gear engaged] Then shift into reverse and repeat. You are listening for a sharp clunk from the differential.  If you hear one, then the right-front differential  mount stud has broken loose from its woefully underdesigned frame attachment."

I tried the above procedure and it does not produce any clunk.   But now my questions, please...       Anybody understand this procedure?   How/why does it work?   And does its not producing a clunk really mean that my diff. mount is OK?

Many thanks, and KEEP SAFE in these difficult times!

Tony

[RogerH]

Hi Tony,

your procedure may well work to find a duff stud.

By engaging 1st gear you twist the diff in one direction. When you go into reverse you twist the diff back the other way.

if the stud had cracked loose then you may well hear the metal rubbing.

As for a clunk after a diff rebuild - I would look at the diff. They are devils to get spot on.  Somebody on here recommended these people in 2018 http://www.testransmissions.co.uk/tes-transmissions-manual-2008.html. They are in the UK so may be awkward for your in France.

 

Roger

[stuart]

IRS cars also suffer with play in the propshaft where the sliding joint section is because the box and the diff are basically fixed unlike a live axle car,

Stuart.

[rcreweread]

35 minutes ago, stuart said:

IRS cars also suffer with play in the propshaft where the sliding joint section is because the box and the diff are basically fixed unlike a live axle car,

Stuart.

Stuart - wouldn't worn propshaft splines show up as a clonk in the test Tony did?

If I understand the test correctly, it should show up a cracked mounting pin but I can't see why it wouldn't also show up any clonks in the diff and the driveshafts - the only place it wouldn't show up any potential clonks is in the wheel hubs, as they would be the only bits locked solid by the application of the brakes. As there were no clonks in the test, that surely points to the wheel hubs - are they wire wheels?

Confused and cheers Rich 

[tonycharente]

45 minutes ago, RogerH said:

As for a clunk after a diff rebuild - I would look at the diff. They are devils to get spot on.  Somebody on here recommended these people in 2018 http://www.testransmissions.co.uk/tes-transmissions-manual-2008.html. They are in the UK so may be awkward for your in France.

Roger

Thanks Roger,

Thanks to the enormous help and advice from the late Alec Pringle and the expertise of Peter Cox I had my original axle back in the car a couple of years ago, fitted by Peter with a 3.45 diff. which I find to be ideal.  The axle came back very quiet with no clunks, so I am hoping that it's not that, but even if it is I can live with that.   In fact the only thing that really worries (worried?) me is (was?) the possibility that it might be the rear axle departing company with the chassis...

Cheers

Tony

 

 

[tonycharente]

22 minutes ago, rcreweread said:

Stuart - wouldn't worn propshaft splines show up as a clonk in the test Tony did?

If I understand the test correctly, it should show up a cracked mounting pin but I can't see why it wouldn't also show up any clonks in the diff and the driveshafts - the only place it wouldn't show up any potential clonks is in the wheel hubs, as they would be the only bits locked solid by the application of the brakes. As there were no clonks in the test, that surely points to the wheel hubs - are they wire wheels?

Confused and cheers Rich 

Thanks Stuart and Rich,

Yes, Rich, that's the bit I don't understand either  -  why would the procedure not equally produce a clonk with just about any of the other causes? 

Including in fact my wire wheel splines.  Rich, why would these not also produce a clonk?  Or is that not what you meant when you said "that surely points to the wheel hubs"?

Thanks

Also confused...

Tony

Edited April 16, 2020 by tonycharente

[Z320]

Hi Toni,

how did you tighten your wire wheels?

I know people LOVE complicates issues, but maybe the problem is very easy to solve 

Ciao, Marco

Edited April 16, 2020 by Z320

[rcreweread]

20 minutes ago, tonycharente said:

Thanks Stuart and Rich,

Yes, Rich, that's the bit I don't understand either  -  why would the procedure not equally produce a clonk with just about any of the other causes? 

Including in fact my wire wheel splines.  Rich, why would these not also produce a clonk?  Or is that not what you meant when you said "that surely points to the wheel hubs"?

Thanks

Also confused...

Tony

Tony - with the brakes fully applied, which takes place in the drum, anything beyond the drum can't move, so you would only notice clonks from your wire wheel hubs if the brakes were not applied. All the parts the inward side of the brake drum are free to move (when the brakes are firmly on) with the engine trying to drive the driveline - the 1st and reverse engagement will create a sort of "rocking" to emulate the torque which ultimately breaks the diff mounting, but it will also twist the propshaft, the diff and the driveshafts - in other words the whole of the drivetrain so if there was any potential clonking play in those components, I would expect it to show up during the test.

Does that make sense?

Cheers  Rich

[tonycharente]

5 hours ago, rcreweread said:

Tony - with the brakes fully applied, which takes place in the drum, anything beyond the drum can't move, so you would only notice clonks from your wire wheel hubs if the brakes were not applied. All the parts the inward side of the brake drum are free to move (when the brakes are firmly on) with the engine trying to drive the driveline - the 1st and reverse engagement will create a sort of "rocking" to emulate the torque which ultimately breaks the diff mounting, but it will also twist the propshaft, the diff and the driveshafts - in other words the whole of the drivetrain so if there was any potential clonking play in those components, I would expect it to show up during the test.

Does that make sense?

Cheers  Rich

Hello to Marco and Rich,

>>> Marco,  I tighten my wire wheels by hitting the spinners really hard with a proper Thor hammer  -  that (regretably) is not the problem.

>>> Rich,   Thank you for your excellent explanation making it all clear even to me.  This afternoon I pulled the hand-brake on really hard (and yes it does work - I have the extenders!), jacked both rear wheels off the ground and pushed and pulled on each wheel and turned it,  all as hard as I could in all directions.  Not the slightest bit of movement felt, so I ruled out wire-wheel splines, thank you.  Then (jacking the car higher and inserting axle stands...) I crawled underneath LEAVING THE HAND-BRAKE ON (not tried it like that before, thank you) and could find no play in either the drive shaft UJ's or the prop shaft UJ's.  However holding onto the prop UJ I was able very easily to turn the diff output shaft  - by about 3 mm measured at the circumference of the prop shaft UJ circular part.   

So I am delighted to have identified the problem, thanks to you all, relieved that it's not the diff mounting pin problem, but surprised by the amount of play in the diff.  The car has done 2600 miles since the diff was rebuilt.  

New question : do you think this much play is "normal" ?   I've not tried to work it out, but it's not many degrees...   Should I be worried ?

Thanks to all,

Tony

Edited April 16, 2020 by tonycharente

[rcreweread]

Tony - in my non expert opinion, I don't think 3mm play is very much, and I would have thought, not much to worry about - i've seen a lot worse than this without any obvious side effects but I'm sure someone with more expert experience than me will be along to comment shortly.

In a way, not what you wanted to hear, as you now still may not know what is causing your clonk - Have you checked both ends of the propshaft to make sure the ujs are all good and tightly bolted up?

Cheers Rich

[tonycharente]

On 4/16/2020 at 5:53 PM, rcreweread said:

In a way, not what you wanted to hear, as you now still may not know what is causing your clonk - Have you checked both ends of the propshaft to make sure the ujs are all good and tightly bolted up?

Cheers Rich

Thanks Rich.

Today I jacked my car up again, with the hand-brake hard on, but this time with it in first gear, as opposed to neutral.  I then crawled right underneath and grabbed the front end of the propshaft.  I couldn't feel any play anywhere at all  -  and I couldn't turn it at all.   Ditto at the rear end of the propshaft.   I then put it into neutral and tried again at the rear end of the propshaft and was able to rotate it, as yesterday.  This time I did my best to measure the diameter of the circular flange where the propshaft U.J. is  -  +/- 100 mm, and also to measure the amount of rotation better  - +/- 5 mm (not 3 mm as estimated yesterday.  Applying what remains of my schoolboy maths I make that a rotation of just under 6 degrees.

Based on the above I am thinking that my clonking IS coming from the diff (???)

Any more thoughts on degrees of free play, please?  It seems to me to be a bit high, but the axle is very quiet...

Many thanks

Tony

 

[Tom Chatterley- Cox]

On 4/18/2020 at 5:14 PM, tonycharente said:

Any more thoughts on degrees of free play, please?  It seems to me to be a bit high, but the axle is very quiet...

Hi Tony,

We have just measured one of our rebuilt ones and they are roughly 3mm at the flange which equates to 0.007" of backlash on the crownwheel as per the workshop manual, so 5mm is a bit excessive but isn't terribly alarming as far as diffs go, well within acceptable limits.

Not sure if anyone's recommended checking brakes, as light drag will cause a clunk under the circumstances you mention. If you wind the adjustment pins on the backplates back 2 clicks each side,  to slightly slacken the shoes and if you haven't already, my Dad recommends 90/140 Mild EP as modern EPs have a far lower viscosity (even more important if you're in sunny France!) although they claim to be higher.

Look forward to your reply.

Tom Cox

(Son of Pete)

 

[badhuis]

The IRS is one of the reasons I choose NOT to buy a TR4a but a TR4 instead 27 years ago.

My Herald at the time ate U/Js every few months it seemed and my 2000 Mk2 was not without problems at its rear end too.  

[tonycharente]

4 hours ago, badhuis said:

My Herald at the time ate U/Js every few months it seemed  

Must have been all that power  !!!

[tonycharente]

On 4/21/2020 at 1:38 PM, Tom Chatterley- Cox said:

Hi Tony,

We have just measured one of our rebuilt ones and they are roughly 3mm at the flange which equates to 0.007" of backlash on the crownwheel as per the workshop manual, so 5mm is a bit excessive but isn't terribly alarming as far as diffs go, well within acceptable limits.

Not sure if anyone's recommended checking brakes, as light drag will cause a clunk under the circumstances you mention. If you wind the adjustment pins on the backplates back 2 clicks each side,  to slightly slacken the shoes and if you haven't already, my Dad recommends 90/140 Mild EP as modern EPs have a far lower viscosity (even more important if you're in sunny France!) although they claim to be higher.

Look forward to your reply.

Tom Cox

(Son of Pete)

 

Hello Tom,

Thank you very much for looking into this  -  and for the very helpful and reassuring comments.

Today I jacked up both rear wheels at once to see how freely they span.  Possibly the very slightest bit of drag on the right-rear.  I backed off the adjustment pins on both sides,in line with your suggestion and then took her for a run.  (Officially to go and get cash out of the bank - we have "proper" lockdown here, requiring the completion of a signed, dated and timed form giving the reason for going out each and every time you go out...    ...and proper fines if you don't comply).  

It may just be wishful thinking, but it did seem to clonk less readily, thank you  I will need to wait until the end of lockdown here is over in order to  go for a spin with my wife on board as she's very very good at identifying noises, but meanwhile I'll try to find something else to worry about !!!

Your father very thoughtfully fitted a diff. drain plug, and it is about time I did change the diff oil.  Are you able to recommend a particular brand of 90/140 Mild EP please?   I used Castrol EP90 following the rebuild.

Many thanks,

Tony

 

 

 

[johnwill]

On 4/22/2020 at 5:47 PM, tonycharente said:

with my wife on board as she's very very good at identifying noises.....

I was driving my 4A from Coventry to Swindon on a lovely summers day, and had a persistent "squeaking" noise that was getting to me. We know the squeaks and rattles our cars usually make, and this was a new one. Kept checking different things en route, to see if anything i touched stopped it. The wife didn't hear a thing, and assured me I was imagining it.

We stopped at Burford for a bite to eat, so i decided to check a few more things while stationary. Couldn't find anything obvious, so decided to get back on our way. As my wife got back in the car, I heard the squeak again....!! It was her bloody earing..!!!!  And she couldn't hear it.. The open top driving kept the damn thing moving a lot, so persistent.

Suffice to say, our wives are very different

 

 

[RogerH]

Next time John buy her Golds ones.

Those wrought iron cheap things squeak something chronic  

 

Roger

[tonycharente]

12 minutes ago, johnwill said:

"Suffice to say, our wives are very different "

Reminds me of the one about the loud shrieking noise coming from the passenger side of the car when cornering really hard and almost going off the road....       ....THAT only happens with a lady passenger too !!!!!