Zulu 10 wrote:

Please forgive me if I have got a firm grasp of the wrong end of the stick, but when you say "no way of setting bearing loads correctly" I presume you mean no way with diff in the vehicle. I know that it's a PITA but have you considered removing the diff and taking it to a specialist?

The place I have in mind is BGH Geartech in Cranbrook - assuming that Brian is still alive of course, God bless him, irascible doesn't do just to him, but he's the only person that I trust with my competition car diffs.

Have a look at this http://www.fullfatrr.com/forum/topic39560.html

Basically you need the LR special jig to hold the diff in the right angle, and then you need the LR torque tool to measure the torque when the pinion is rotated and you have to gradually load the bearings... if at any point you go over... strip it out, throw away the collapsible spacer and start again.

And then it gets better... As far as I know this bit of kit will not work with the early style pinion coupling and will only work with the new flange type.... so your in to £800 before you start  Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

I would buy a second hand diff and prop off an internet auction site that already have the flange drive done and swap them out with yours fluid change for the diff and new drive shaft oil seals if your that bothered probably the cheapest solution , I feel your pain as this same thing happened to my td6 in 2011 sat at a roadside with no drive , but as it was already booked in to get the recall done but had been postponed 2 or 3 times due to lack of parts ,I had it recovered to the dealers and landrover did it for free !
Prop less than £100 diff about £200

Don't get me wrong, the car has been fixed, with a new old style coupling, but as there is no way of torquing the coupling it was a case of best guess....... how long best guess lasts is anybodies idea.... the S/H diff and prop will be the next thing should the worst happen.... but finding a TD6 diff that's been modded isn't as easy as it sounds.... there are plenty of V8's but I think they are a different ratio  Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

There are several of the mod'd diffs on eBay now and plenty of props , if you've fixed it happy days

miggit wrote:

Zulu 10 wrote:

Please forgive me if I have got a firm grasp of the wrong end of the stick, but when you say "no way of setting bearing loads correctly" I presume you mean no way with diff in the vehicle. I know that it's a PITA but have you considered removing the diff and taking it to a specialist?

The place I have in mind is BGH Geartech in Cranbrook - assuming that Brian is still alive of course, God bless him, irascible doesn't do just to him, but he's the only person that I trust with my competition car diffs.

Have a look at this http://www.fullfatrr.com/forum/topic39560.html

Basically you need the LR special jig to hold the diff in the right angle, and then you need the LR torque tool to measure the torque when the pinion is rotated and you have to gradually load the bearings... if at any point you go over... strip it out, throw away the collapsible spacer and start again.

And then it gets better... As far as I know this bit of kit will not work with the early style pinion coupling and will only work with the new flange type.... so your in to £800 before you start

As above it's nothing that can't be jury rigged to do, you are just setting the pre-load based on the rotational torque resistance of the pinion shaft in the bearing (4Nm).

If you've ever done the steering swivels on a Land Rover then it's virtually the same, you use shims to set the pre-load on the swivel so you get x amount of pull measured with a spring balance (equivalent of torque).
You could easily do the same with a spring balance or a fixed weight at a certain distance and working out the moment (4Nm = 0.4kg/m) which looks to be the way LR do it albeit with a fancy tool.

To be honest just live with what you've done, if it fails then just stick in a 2nd hand diff and prop.

I'm afraid that you haven't looked at what your dealing with....

the coupling looks like this



Looks like this on the diff



So could you please tell me how you bolt on an arm to measure the torque? also how long does the arm have to be? The laws of physics dictate that the longer the lever the easier the work, so without the correct length arm there is no way to get an accurate reading And there is no way of fixing it to the diff

The replacement coupling looks like this, arm attachment is easy.....



Oh and that's the back at the top, prop bolts on to the 6 holes at the bottom of pic  Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

Honestly I do understand exactly what we're dealing with here.

All that we’re trying to measure here is what I will crudely describe as a friction force i.e. the very small amount of torque required to rotate the pinion in its housing – it’s no different to doing any other form of opposing taper roller bearing such as a wheel bearing, although we generally do those by end float.

You don’t necessarily have to bolt on anything to measure the torque figure: a length of 25 x 3mm steel bar with the last 50mm bent through 90º and then attached to the coupling with a couple of jubilee clips would suffice.

The preload torque is so small at 1.4Nm that you’re not going to unseat the clips.

I’m unsure whether I understand your question “also how long does the arm have to be”, because the length of the bar is unimportant so long as you know the distance between the axis and the point where the load is applied.

The point about torque is that it simply defines a moment which means that 1.4Nm can be achieved by a force of 1.4Newtons at a distance of 1 metre or 14 Newtons at a distance of 100mm: the result is the same.

Basic physics defines F = ma where F= force, m = mass and a = acceleration.

To determine the vertical force which results from a given mass just substitute g (9.81N/kg) for a.

For example if I (mass 92kg) hang from a horizontal bar at a point 2metres from the pivot I will produce a moment of 2 x 92 x 9.81 or 1805 Nm.

If I’m told to do a nut up to 200Nm then I know that I can achieve that using a bar that is roughly 11% of that length.
N.B. That is when I hang vertically from a horizontal bar.

In your case, if you drill a hole in the aforementioned bit of 25mm x 3mm bar at a distance 300mm from the axis of the coupling then you need a spring balance pull of a little under half a kilo to generate the correct torque.

I knew that Isaac Newton was lurking on this site somewhere

I understand what your saying, sort of... was a lot easier with the swivel hubs on a Landy cos you put a spring balance on the steering arm and pulled (about 7lbs if I remember correctly) As there was no description of the special tool and spring rates it sort of went over my head..... If some one says put a 300mm bar on the diff and pull at xx kgs that is great. I do realise that the length of the bar is irrelevant, but the fixing distance from the centre of the diff is critical. And you are right a bent bit of tin and some jubilee clips should do the job, along with the use of a vice.

This info isn't out there, so it's a bit hard to work out what to do.... while it's not beyond most peeps, removing a diff and lashing up a jerry build rig... working out the best way of getting the correct rotational force is a real head ache.... I was asleep during that lesson  Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

miggit wrote:

I was asleep during that lesson

I can probably relate to exactly why you were asleep, but don't get me started on the quality, or lack of it, of the teaching of mathematics and engineering skills in this country.

I remain convinced that most mathematics teachers don't understand how to practically apply it to the real world, and that most people think that the engineering skill means the ability to use CAD/CAM. What they 'don't get' is the need for people to have a 'feel' for what feels right.

Frankly needing half a kilo on the end of a foot rule to rotate a new pinion mentally feels a bit tight to me, that said of course that is with the crown wheel already installed, so that will inevitably blur the accuracy...

My late father was an old school mechanical engineer so he'd taught me all about the principles of moments in my early teenage years, so other than having to unlearn lbfft and learn Nm I was asleep in Physics 'cos Dad had already taught me.

At this point of course someone will come along and point out that what I typed last night after a couple of glasses of Pouilly Fumé is all complete bolloeaux because I got a decimal point in the wrong place...

Edited: Have just read what you wrote "but the fixing distance from the centre of the diff is critical" and no, it isn't, what matter is the distance between the centre of the pinion axis and the point where the force/load is applied. It matters not whether you use jubilee clips to affix your bar to the approx 40mm sleeve of the old style fixing, or bolts to affix a bar to the 100mm diameter flange of the revised style coupling, so long as you know the distance from the rotational centre to the load point. Does that make sense?

Hopefully this will explain how Torque T1 = F1 x d1 and T2 = F2 x d2 and to get the same torque either variable can be manipulated.
N.B. I've used F for force rather than m for mass on the diagram which will probably upset the purist - just remember that Force is roughly ten times mass.

The pinion must be rotating continuously when you measure the preload torque. Just wrap a piece of string around the splined drive tube (whose diameter you can simply measure to determine the radius) several times and attach the end to a spring balance and pull.

Phil

I must admit that I'd only ever seen/heard of it being done using a lever arm and spring balance, but the string technique is very elegant, and could possibly be done in situ, so long as the output shafts are disconnected?

Edited to correct my stupidity - couldn't be done in situ, because of the presence of the crownwheel with no way of accurately compensating.

Last edited by Zulu 10 on 30th Sep 2016 9:24am. Edited 1 time in total

I like that string method, over comes the inertia and rotation issue

As the 'official' method is done without anything installed except obviously the pinion shaft/gear then I would have thought you would have to do the same. The extra drag of the crown wheel/output shaft bearings will add to the drag even if the shafts are removed and give a false higher reading?
Then again those bearings, although look to be taper bearings, don't have a preload other than provided by the casing torque specs.

Thoughts?

Just been back to skool, lost me at Hello

Is it just me, or does the goal posts keep moving? from a rotational force we are now at a constant rotational force, that is not as easy to be accurate with. Although wrapping a bit of string around the coupling and measuring the pull, is actually easier than the attaching a lever......

So we now have the string wrapped around the coupling, and anchored with a jubilee clip.... so how hard do you have to pull to get the correct setting? And then from that answer we can work out how strong both you and the string have to be

FYI the coupling is exactly 55.00 mm in diameter Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

Weejock wrote:

I like that string method, over comes the inertia and rotation issue

As the 'official' method is done without anything installed except obviously the pinion shaft/gear then I would have thought you would have to do the same. The extra drag of the crown wheel/output shaft bearings will add to the drag even if the shafts are removed and give a false higher reading?
Then again those bearings, although look to be taper bearings, don't have a preload other than provided by the casing torque specs.

Thoughts?