best way to get prop bolts undone..

[512BB]

You do not need heat to separate the 2 flanges. Just tap harder on one flange or use a sharp cold chisel and bolster in between the 2 flanges and they will come apart. Just a bit of stickschon holding them together.

'the propshaft complete can be removed with the engine in situ'

Yes, I am aware Hawksfield, but thanks for mentioning it.

Leslie

[mbell]

There maybe a bit of sealant on the flanges to stop any oil that is leaking down the pinion shaft coming out. As suggested I wouldn't use heat, just hit it a bit hard or use suitable tools to try split them.

[2cams70]

There maybe a bit of sealant on the flanges to stop any oil that is leaking down the pinion shaft coming out. As suggested I wouldn't use heat, just hit it a bit hard or use suitable tools to try split them.

You shouldn't have to use any sealant. The root cause of the problem is that the pinion bearings have lost their preload and the flange nut has come loose. Later diffs were an improved design having both a collapsible spacer and pinion retaining nut of sturdier construction.

To fix it properly you need to remove the flange and the pinion oil seal, replace both the collapsible spacer and pinion nut with improved design ones and reset the pinion preload - by which stage you may as well pull the diff and give it a complete refresh!

[512BB]

2 cams wrote 'You shouldn't have to use any sealant'

You shouldn't have to use any sealant on the flanges, but any self respecting diff rebuilder will use a sealant on the splines of the input flange and some sealant on the back of the nut, all areas having been degreased first. I know some rebuilders don't like to see any sealant on their nuts

2 cams also wrote 'The root cause of the problem is that the pinion bearings have lost their preload and the flange nut has come loose. Later diffs were an improved design having both a collapsible spacer and pinion retaining nut of sturdier construction'

I do not agree, as the pinion bearing loosing its preload because the pinion nut has come loose has nothing to do with sealing and keeping oil in the case. And if the pinion bearings had lost their preload and the retaining nut had come loose, then the diff would have been whining and the OP does not mention that.

2 cams also wrote 'To fix it properly you need to remove the flange and the pinion oil seal, replace both the collapsible spacer and pinion nut with improved design ones and reset the pinion preload'

Again, I disagree. You are not going to fix oil running down the splines by replacing the pinion oil seal, crush spacer and a new nut!. As I have previously stated, to fix oil in the void between the 2 flanges you need to undo the pinion nut and remove the flange, clean up, use sealant of choice, and do up the nut to about 36 lbs. I did exactly this on one of my cars many years ago because the diff had started to whine. Bastard of a job to get a socket onto the nut though, but managed it.

Where I do agree, is that the whole job is a lot easier on the bench and anyone who can replace that oil seal properly, in situe, is a better spanner man than me.

For your delectation 2 cams viewtopic.php?f=33&t=18555

Leslie

[Andy8421]

While it isn't a first class solution, for a diff which is otherwise fine, what is the problem in sealing the diff flange to the propshaft flange with sealer to avoid a leak down the splines?

At first sight (apart from a bit of oil between the flanges) it seems an easy fix.

[512BB]

Nothing wrong with that at all. In fact, if the 2 flanges are in good order and flat, they practically seal themselves, so if the 2 flanges were cleaned and coated in wellseal, they would almost certainly form a dry seal. Just do the bolts up nice and evenly and away you go.

So just a little heads up to anyone who's diff starts to whine, as one of mine did many years ago, when it had been running silently, just try tightening up the input flange nut as tight as you can get it, and that may be all the problem is. You will not be able to get a torque wrench on it.

Leslie

[2cams70]

You can slop as much sealant as you like over the propshaft and diff flanges but it's a bodge. A diff with the pinion preload set correctly, using the later type collapsible spacer (all the spacers supplied these days are to the later design) and the later type pinion retaining nut (again all the nuts supplied new these days are to the later design) will not leak oil from the splines. No sealant required whatsoever.

Ford implemented the design change to the spacer and the pinion nut sometime around 1973 (on Escorts at least). I do have examples of the early and late type nut but at this point i can only find an example of the later type spacer and not the early one amongst my collection of junk. If I manage to find one I'll post pictures to explain and then it will hopefully be clear to all the correct way to cure oil leaking from the pinion splines and loss of loss of preload on the pinion bearings (i.e that is use the latest specification parts and reset the pinion preload using correct tools)

[512BB]

A few points. Nobody said slop sealant anywhere. Nobody said that putting a smear of wellseal on both the flanges was ideal, but to save removing the diff at that time, it is a workable solution if the right conditions are met. Indeed, the OP has not even reported that there is / was a release of oil when and if the 2 flanges are / were separated. I just mentioned that there MAY be a release of oil when the 2 flanges are separated, and something to watch out for.

If using such a temporary sealing method is crap, that does not say much for the sealing of the backplate to the engine block, re the oil feed to the timing chain, where exactly the same method of sealing is used, save for a paper gasket in between. Seems to work alright there, if done correctly, and that area is under 40 psi of oil pressure, whereas the diff internals are under no pressure, at least not if the breather is clear. Indeed, any metal to metal faces that needed to be oil tight would be bodge, according to 2 cams, for example the front cover to backplate.

2 cams wrote ' A diff with the pinion preload set correctly, using the later type collapsible spacer (all the spacers supplied these days are to the later design) and the later type pinion retaining nut (again all the nuts supplied new these days are to the later design) will not leak oil from the splines. No sealant required whatsoever.

Ford implemented the design change to the spacer and the pinion nut sometime around 1973 (on Escorts at least). I do have examples of the early and late type nut but at this point i can only find an example of the later type spacer and not the early one amongst my collection of junk. If I manage to find one I'll post pictures to explain and then it will hopefully be clear to all the correct way to cure oil leaking from the pinion splines and loss of loss of preload on the pinion bearings (i.e that is use the latest specification parts and reset the pinion preload using correct tools)'

I have built well over 40 diffs, see previous link, from a huge collection that I bought many years ago, and the only differences I noticed between them were in the flange seals, early ones were actually leather !!!!!! and differences in the design of the crush spacer. I do not recall any change in the design of the flange nut. So I am eager to learn and look at these later spacers and flange nuts that somehow stop oil travelling down the splines and then leaking out.

Leslie

[rgh0]

Use of sealants on metal to metal components that will stop oil leaking out is normal good engineering design practice. It is not a bodge. The Ford design implementation without a sealant is the bodge that relied on new components to get through the warrantee period. Plus the rest of the oil leaks made any diff flange leak trivial

cheers
Rohan

[2cams70]

Please see picture below. From left to right we have late design crush tube, early design pinion nut, late design pinion nut. As previously advised I don't currently have an early design crush tube (apologies for that) but suffice to say the wall thickness is much less than the late design one.

Fact 1 - the crush tube design change:
Increasing the wall thickness has the effect of increasing the clamping force that exists between the front taper roller bearing inner race and the pinion flange for any given set value of pinion bearing preload. In other words you need to tighten the pinion nut to a higher torque value in order to adequately crush the tube the correct amount and consequently achieve the correct pinion bearing preload. The increased clamping force reduces the chance of oil leaking between the two surfaces and into the mating splines of flange and pinion shaft from the inside. Similarly the increased clamping force also reduces the chance of oil leakage between the underside of the flange nut and the flange itself on the outside.

Fact 2: - the pinion nut design change
The improved design flange nut is much thicker and therefore stiffer in the upper portion that is deformed to provide the thread locking effect. This means the friction (and hence the locking effect) between the mating threads is greater compared to when the earlier design nut is used.

Finally some more on the subject of using a sealant on the splines. Aside from the fact that it isn't required (Mk2 Escort diffs fitted standard with the upgraded parts rarely develop leaks in this area) a sealant is not going to work long term. There is always a small clearance existing between the mating splines and the contact pressures between them is very high. Movement between the splines from drive/coast torque reversals (no matter how small) and high contact forces mean that any sealant is likely to be eventually forced out from between the surfaces at which point you will be back in the same place as you started.

[rgh0]

So Ford modified the crush tube and nut to try to stop oil leaks. Did they succeed for the rebuilding of 50 year old diffs ? maybe ...may be not. The right sealant will just fill the micro gaps between the metal to metal contact of the splines and the nut flange, how long it will last is debatable but if the splines are moving and the flange and nut moving relative to reach other then you have bigger problems than an oil leak.

cheers
Rohan

[2cams70]

So Ford modified the crush tube and nut to try to stop oil leaks. Did they succeed for the rebuilding of 50 year old diffs ? maybe ...may be not. The right sealant will just fill the micro gaps between the metal to metal contact of the splines and the nut flange, how long it will last is debatable but if the splines are moving and the flange and nut moving relative to reach other then you have bigger problems than an oil leak.

The main reason Ford changed the crush tube and lock nut design of course was to better maintain the pinion bearing preload over time. The elimination of oil leaks from the splines was just a secondary effect. The earlier crush tube collapsed over time and so the pinion bearings lost their preload, the clamping force on the flange was consequently lost and leaks developed from the splines.

I've pulled many original diffs from Mk2 Escorts in my time and even after 40 or so years there's still some preload in the pinion bearings and no leaks. The same cannot be said for earlier diffs with the earlier crush tube and nut.

If you have a diff with the later design crush tube and nut and it's still leaking from the splines the reason is because you have set the pinion bearings with too little preload or the pinion bearings have become worn (unusual for these diffs if the oil level is maintained). It's not because you need sealant on the splines.

By nature there must be a very small clearance between the splines. It's not designed to be entirely rigid. Imagine driving hard in reverse and then hard forward. The splines must move a little as there's only the friction force from the nut preventing them from doing so. Under these conditions regular sealants won't cope.

The other possible cause is of course that the replacement crush tubes you buy these days may look ok but may not actually be ok and the crush characteristics are different to the original. That will cause you all kinds of problems. I’ve only ever used NOS original ones of the later design

[512BB]

2 cams wrote 'Similarly the increased clamping force also reduces the chance of oil leakage between the underside of the flange nut and the flange itself on the outside.'

I do not think my customers for rebuilt diffs would be overly impressed if I told them I have reduced the chance of an oil leak. I guarantee no oil leaks by using appropriate sealants.

2 cams wrote 'on the subject of using a sealant on the splines. Aside from the fact that it isn't required (Mk2 Escort diffs fitted standard with the upgraded parts rarely develop leaks in this area)

Again, I do not think my punters would be to impressed if, on that rare occasion, they had a diff that developed a leak, which is why I use appropriate sealants.

2 cams wrote 'a sealant is not going to work long term. There is always a small clearance existing between the mating splines and the contact pressures between them is very high. Movement between the splines from drive/coast torque reversals (no matter how small) and high contact forces mean that any sealant is likely to be eventually forced out from between the surfaces'

The first lot of diffs I rebuilt must be what, 10 years ago. Please speak up anybody who bought one of my rebuilt diffs that now leak from behind the flange nut.

You have been told 2 cams, by 2 eminent engineers, well by me anyway that sealant is required to stop oil leaks from the flange on an English diff, but somehow, I just know that we are not going to get through, and very shortly, you are going to be asked to leave the forum for spreading a load of twaddle remember that one.

So good people, take your pick as to who you have your diff rebuilt by. 2 cams, where I can assure you, you will need wear your galoshes in the garage, or by my goodself. In which case you can continue to wear your carpet slippers in your workshop, at least towards the back of the car.

I attach a couple of pictures to show early crush spacers, and late.

Fin

Leslie

[Craven]

2cams70
You wrote:-
Fact 1 - the crush tube design change:
Increasing the wall thickness has the effect of increasing the clamping force that exists between the front taper roller bearing inner race and the pinion flange for any given set value of pinion bearing preload. In other words you need to tighten the pinion nut to a higher torque value in order to adequately crush the tube the correct amount and consequently achieve the correct pinion bearing preload. The increased clamping force reduces the chance of oil leaking between the two surfaces and into the mating splines of flange and pinion shaft from the inside. Similarly the increased clamping force also reduces the chance of oil leakage between the underside of the flange nut and the flange itself on the outside.

Only level of clamping force involved is that which produces the correct friction between the elements, it will be the same force whether old or modified tube or nut are used. I understand the modification to the crush tube was to reduce the initial compressing force needed to start the deformation of the tube.

[2cams70]

2cams70
You wrote:-
Fact 1 - the crush tube design change:
Increasing the wall thickness has the effect of increasing the clamping force that exists between the front taper roller bearing inner race and the pinion flange for any given set value of pinion bearing preload. In other words you need to tighten the pinion nut to a higher torque value in order to adequately crush the tube the correct amount and consequently achieve the correct pinion bearing preload. The increased clamping force reduces the chance of oil leaking between the two surfaces and into the mating splines of flange and pinion shaft from the inside. Similarly the increased clamping force also reduces the chance of oil leakage between the underside of the flange nut and the flange itself on the outside.

Only level of clamping force involved is that which produces the correct friction between the elements, it will be the same force whether old or modified tube or nut are used. I understand the modification to the crush tube was to reduce the initial compressing force needed to start the deformation of the tube.

Leslie. It really is not my intention to cause offence with suggesting an alternate reason for the oil leak and why you don't need sealant. I see you have two examples of the earlier crush tube in your photo. Appreciate if you could kindly measure the wall thickness of these tubes and advise. I don't have an example in my possession.

Craven - A thicker, stiffer crush tube will require more torque on the pinion nut to crush and to reach the correct preload on the pinion bearings than a thinner softer one will it not? More torque required on the nut means more tension in the assembly and more tension in the assembly means less chance of oil leakage between the flange and the pinion bearing inner race - correct or not?

Any two metal surfaces pressed together will seal without sealant if the force per unit area between them is high enough (well I think so - quite willing to be proven wrong!)

I'm quite willing to be proven wrong because I like learning things. I too am a university qualified engineer by the way although according to you guys the "eminent" title probably doesn't apply!!

Unless you actually have really loose pinion bearings (i.e end float) you are unlikely to notice increased diff noise from incorrect adjustment. The main effect will be reduced pinion bearing life (and oil leakage if you don't use sealant).