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play in my IRS diff


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Hi,

with the new oil in (a GL4/5 for vehicles with gearbox-differential unit) the play is "0", I'm very pleased.

Not pleased I am about the diff back in the car again. It always was slightly "wedged" upwards to the front, and this it is again.

Something must be wrong.....

Looking on the sketch the upper front PU mount (79) seem to be more solid than the ones on the rear (70), and that could solve the problem.

Apart from (80) which I have to cut shorter.

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The sketch is from Rimmer (thank you), but the order numbers are the same. Same at other suppliers.

Any idea anyone what's wrong? Thanks in advice.

Marco

 

 

Edited by Z320
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Back from my garage, with the diff on the workbench again and a bubble level under the car I ask myself: who wants to fool me!?

Nothing is in 90° angle and nothing is on the same level! But all looks original!

For a propper fit and a leveled differential the top front PU mounts must be massiv longer,

the lower ones massive shorter, which makes them not elastic anymore!

Time for a basic change.

Edited by Z320
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1 hour ago, Z320 said:

Back from my garage, with the diff on the workbench again and a bubble level under the car I ask myself: who wants to fool me!?

Nothing is in 90° angle and nothing is on the same level! But all looks original!

For a propper fit and a leveled differential the top front PU mounts must be massiv longer,

the lower ones massive shorter, which makes them not elastic anymore!

Time for a basic change.

They dont sit level anyway.

Stuart.

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Hi Stuart, +/- 1° is not the issue.

This is the diff with the ingoing flange leveled vertical.

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You see the front cossmember falling - or raising - how you want, the coned PU-mount levels it again.

And on the rear the PU mount with the same high is about 3 mm too low - 3 mm on 340 mm distance is OK, that's only about 0.50°

This is not OK! Is the front mount original welded like this on a 4A? The bold looks scarred rusty and original.

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The difference is about 4°, the result is this, all 4 nuts the same way not tight.

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And this is what I want, with the front end considerable lowered.

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(the hex bar is a bolted fast and easy provisional repair - since years, don't mind).

Ciao, Marco

 

 

Edited by Z320
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I dont have an IRS 4a here but these pictures may help you a bit from a 5 so basically the same mounts

Stuart.

 

Marks TR5 095.jpg

Marks TR5 642.jpg

Edited by stuart
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Thank you Stuart,

and there are no problems to fix the diff in the frame?

Only the 4A has a special aluminum bracket bolted on the diff,

TR5-6 is different and perhaps this solved the problem.

In this case - it would only effect TR4A with IRS axle.

Ciao, Marco

 

 

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Hi Marco,

iirc my diff (TR6) was not lever either. But after sleeping a night and checking everything again I concluded it is not level per the original design.

Waldi

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Hi Waldi,

with the diff in - indeed no worry. But now it is out and I correct this.

"Horizontal" I only want to have it because the 4 bolts holding it are exactly in the the correct distance as the crossmembers of the diff - and are about vertical.

To bolt the diff not 90° against them means to pull them closer to each other. This hurts me.

To make the parts I need is no a big effort.

Ciao, Marco

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59 minutes ago, Z320 said:

Hi Waldi,

with the diff in - indeed no worry. But now it is out and I correct this.

"Horizontal" I only want to have it because the 4 bolts holding it are exactly in the the correct distance as the crossmembers of the diff - and are about vertical.

To bolt the diff not 90° against them means to pull them closer to each other. This hurts me.

To make the parts I need is no a big effort.

Ciao, Marco

You may get a idea if you look at Racetorations mounts

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Hi,

allow me to shift the titel "play in my diff" slightly.

This is what I want to avoid in the future.

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To make the distancers and connectors was a little job on 2 evenings in my workshop,

there I remembered the pair of "reinforcing clamps" on top of the next photo, stored there the since years.

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I don't know if they will protect the brackets on the frame (still original, not boxed) - but I'm shure they cause no problem.

All parts fixed on the frame and ready to lift the diff in with my new little helper from China - I failed badly!

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I did not get the diff in because the bolts now have the correct lenght (in my opinion) but are too long to get them in the crossmember.

Because the lower edge of the crossmember touches the frame on the red marked positions....

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This is when I noticed: the TR engenieers also failed to get the diff in correctly!

And instead of proper modifying the frame or the crossmember they went the easy way,

welded the front mount in a higher possition and did not worry about the diff not angular in the frame.

You can see the positiv or not.......

I simply removed the connectors again, fitted the diff with the front crossmember first and and the connectors second.

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On the photo above: my new friend from China, he was a great helper to safe my back and fingers, very much recommended!

This is how it looks like now (nut not tight yet), I hope for a test drive tomorrow.

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Ciao, Marco

Edited by Z320
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Hi Marco,

what is the purpose of the clamped re-inforcing brackets? Reducing flexing of the horizontal section? 
My supports had cracked in the middle of the hor. part (like many shown on here), so it may certainly help to keep that section flatter.

A negative I see is they may also add localised stresses, especially at both ends of the brackets.

Hope your mods work out ok for you.

Cheers,
Waldi

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Hi Waldi,

my only theory is: they make the construction more stiff.

Probably I will never now more about because the brackets are not broken and perhaps never brake.

I see 3 other issues about this bracket braking:

- the way the owner drives the car, I do it touristic

- the diff bending on the 4 bolts dynamic because of too much travel in the rubber mount, mine has PU mounts since 1992 (not the blue once)

-the diff bending on the 4 bolts static because fixed angular (the „short“ housing over longer distance than 90deg.) to the bolts, I cured this 

Ciao, Marco

Edited by Z320
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I had no time for  test drive last week,

so I did it this morning at +2°C because we will have snow the next days and salt on the streets.

I'm very pleased, this annoying CLONK from time to time has gone and the car drives with remarkable less jercking on low speed / load.

After 1 h test drive the diff was still sealed and was only "warm" (no wonder at 2°C outside).

I should have done this repair already 5 years ago - but I have been asking the wrong persons and did not trust on my own assessment.

Ciao, Marco

Edited by Z320
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  • 1 month later...

Guys, very interesting post. I’ve just put new mounting brackets on my front diff bridge and a whole new rear diff bridge bracket, everything was jigged and fit together very nicely on test fitting, the mounting posts are parallel and the diff just slipped on. I did notice though that the diff isn’t level, I just test fitted the the full drivetrain and unsurprisingly given that the diff isn’t level the drive train as a whole doesn’t run in one plane, in other words the driveshaft doesn’t run straight through the UJs. I have a parts car so checked that and it’s the same, I note here that Stuart said the diffs aren’t mounted level so I’m assuming based on all of that that this is all as original. 
I would have thought that it was desirable in terms of energy loss and possibly even vibration that the driveshaft be as close to running true through the UJs in a plane with the centre of gearbox and differential input/output shafts. Is this not the case or why isn’t the diff level? Is there any benefit in modifying to correct this, assuming it is as per OEM now of course.

FE9C323E-9196-45BC-9C72-9C639FA201AC.jpeg

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Designed like that.

There needs to be a slight angle for the prop shaft to drive on at the diff flange.   It makes the uj rollers work and roll as they are designed.

if not….

The wear that will happen is called Brinnelling and is caused by the roller bearings acting on one spot instead of 'rolling'. With a bit of angle on the UJ’s, the rollers rotate around the bearing case.

 

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11 hours ago, BlueTR3A-5EKT said:

Designed like that.

There needs to be a slight angle for the prop shaft to drive on at the diff flange.   It makes the uj rollers work and roll as they are designed.

if not….

The wear that will happen is called Brinnelling and is caused by the roller bearings acting on one spot instead of 'rolling'. With a bit of angle on the UJ’s, the rollers rotate around the bearing case.

 

+1 there's normally a complimentary angle on the U/J gearbox flange on the other end of the shaft also.

Mick Richards 

Edited by Motorsport Mickey
Clarification.
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Posted (edited)

Hi folks,

very good TRier asked that, it reminded me today on a video I've seen years ago at Youtube.

The engine / gearbox unit in our TRs is slightly angled about 5° in the frame (the outgoing flange of the gearbox is lower than the front end of the crankshaft).

For constant velocity of the diff flange, the flanges of the diff and gearbox have to be parallel

--> means the diff has to be angled the same amount as the engine / gearbox unit is angled.

This is why the IRS diff is mounted in the frame as it is and I have to take my alu spacers out again.

I not realised any problem / vibration until now, but I did not drive faster than 90 km/h since fitted.

Sorry me for my @&5$§!!@ writing above and for any irritation I caused, I should have known better.

Ciao, Marco

Edited by Z320
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43 minutes ago, Z320 said:

Another question is,

how is the diff flange angled on the solid axle TRs?

The axle continually moves up and down as the car drives along the road due to suspension deflection.

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8 hours ago, Z320 said:

Doesn’t the car body move op and down by suspension deflection while the wheels and axle are always on the street?

Probably both.

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Posted (edited)

However, 
the rear axle is bolted on the leaf springs in only one possible position (I never worked on solid axle TR)?

Fixed this way the diff flange is angled 90 degrees to the ground or does the ingoing diff shaft point angular up?

Edited by Z320
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