Diff Pegging

[dollythelw]

Ive run maxi halfshafts with GBR 4.75s and they survived, nicely cut gears, very strong but comes with a stiff pricetag, dimensionally they dwarf LR stuff if thats of any help

[smo]

JW has series so very different again, and theres always options to get a FAR STRONGER copmplete std axle ie Tpyota/ Volvo / Nissan / Dana etc, just depends how far you are prepared to go

What is true is that building a stronger LR based axle will costs a lot, and will still be inferior in many ways to some of the USA and other HD axles that you could fit, but its the Ag Factor here that often stops many doing it.

HTH

Nige

Argh - i spent hours reading the mass debate in another thread on this forum yesterday!!! Very in depth but interesting reading. I also found out that the Dynatrac axles from Maddison 4x4 (Dana prorock 60) in defender setup fro front and rear is a mere $14,000 - which i recon after import, shipping and taxes (good ol vat) you wouldnt see change from 10K - thats a fair few upgraded LR axles.

Still, i digress. Thanks for the info Nige (and others), most appreciated.

[Jon White]

Been looking at pics of the pegging. Does anyone know if the slipper pad is actually retained to the adjuster screws in any way, or does it just float, being retained by the dog ends of the screws that sit into machined recesses on the pad???

Does that make sense?

Jon

[smo]

Been looking at pics of the pegging. Does anyone know if the slipper pad is actually retained to the adjuster screws in any way, or does it just float, being retained by the dog ends of the screws that sit into machined recesses on the pad???

Does that make sense?

Jon

It would appear to float, being held in place by the dog screw on one side (or bolt!) and the back of the crown wheel on the other. If you were to fix the pad, by means of say epoxy resin you wouldnt be able to adjust the pressure applied or take up slack caused by wear on the phosphor bronze.

[Jon White]

That was what I thought. It just seemed to me that it would be better engineered if the slipper pad was held say a couple of thou off the crownwheel to prevent wear, such that it would only make contact when under load.

I cant really think of a practical way of doing that however!

Anyone got a good (cheap!) source for the phospor bronze material?

Jon

[Hybrid_From_Hell]

Leeside Tools in Yapton W Sussex

have all sorts of metal lumps and off cuts ?

I go there regularly for a Men only "Retail Theraphy shopping" fix

ring them ask the man and if so we could do a whiz down as I'm due for another fix .....

Nige

[robhybrid]

4.75 ratio is not the problem, its if they are standard lr parts is where the problem is, i run KAM 4.75's and to date they have stood up well, i still plan to peg them at some stage though.

I asked Dave about pegging my 4.75 kam cr&p but was told that due to the thicker crown wheel that Kam use there is not enough room left in the housing to fit the slipper assembly.

My reason for wanting to go pegged was that I have managed to stretch/bend the 11 bolts that hold the crownwheel to the ARB.

I am not running stupid horsepower (slightly tweaked 2.8 izusu) and I am running std rr 10 spline shafts.

If I had been running stronger shafts I think I would be looking at broken crownwheel bolts by now.

[Diff]

That was what I thought. It just seemed to me that it would be better engineered if the slipper pad was held say a couple of thou off the crownwheel to prevent wear, such that it would only make contact when under load.

I cant really think of a practical way of doing that however!

Anyone got a good (cheap!) source for the phospor bronze material?

Jon

I have never tried it, but my own thoughts on the matter are that a slipper pad may not be necessary. My thinking is that it is only under moments of extreme load that the crown wheel will be forced away from the pinion. If this is true, then I would have thought that even if the bolt ends were left 'bare', but set up VERY close to the crownwhweel, they would stop the flex and the contact between the crownwheel and the bolt ends would be momentary. Since there is plenty of oil being flung about, and the back of the crownwheel is smooth, they would do the job fine. I am assuming that there is room to fit at least one large diameter bolt which won't bend easily.

Regards,

Diff

[istruggle2gate11]

That was what I thought. It just seemed to me that it would be better engineered if the slipper pad was held say a couple of thou off the crownwheel to prevent wear, such that it would only make contact when under load.

I cant really think of a practical way of doing that however!

Anyone got a good (cheap!) source for the phospor bronze material?

Jon

I have thought about this in the past, I dont know how Ashcroft set them, but sensible engineering practice suggests leaving a small amount of clearance, so, would it not be possible to fit just a couple of bolts through? So 99.99% of the time they are not touching, but for the milisecond they are required they just touch, I doubt they would bind up, small surface area and all that oil. Ok, small chance of steel rubbing off and contaminating the oils, just an idea.

[istruggle2gate11]

I have never tried it, but my own thoughts on the matter are that a slipper pad may not be necessary. My thinking is that it is only under moments of extreme load that the crown wheel will be forced away from the pinion. If this is true, then I would have thought that even if the bolt ends were left 'bare', but set up VERY close to the crownwhweel, they would stop the flex and the contact between the crownwheel and the bolt ends would be momentary. Since there is plenty of oil being flung about, and the back of the crownwheel is smooth, they would do the job fine. I am assuming that there is room to fit at least one large diameter bolt which won't bend easily.

Regards,

Diff

I have thought about this in the past, I dont know how Ashcroft set them, but sensible engineering practice suggests leaving a small amount of clearance, so, would it not be possible to fit just a couple of bolts through? So 99.99% of the time they are not touching, but for the milisecond they are required they just touch, I doubt they would bind up, small surface area and all that oil. Ok, small chance of steel rubbing off and contaminating the oils, just an idea.

Great Minds an all that malarky!

[Daan]

I asked Dave about pegging my 4.75 kam cr&p but was told that due to the thicker crown wheel that Kam use there is not enough room left in the housing to fit the slipper assembly.

My reason for wanting to go pegged was that I have managed to stretch/bend the 11 bolts that hold the crownwheel to the ARB.

I am not running stupid horsepower (slightly tweaked 2.8 izusu) and I am running std rr 10 spline shafts.

If I had been running stronger shafts I think I would be looking at broken crownwheel bolts by now.

I run kam 4.75s with ashcroft pegged diffs. It involved slightly modifying the slipper pad, but not to fancy. What was very involved was the fact that I had the pegging done with standard diffs and then changed to different CWPs and diffs. The dia of the diffflanges are different and I had to turn them down.

By the way, the slipper pad is not supposed to touch in normal use.

daan

[B reg 90]

I run KAM 4.75 ring and pinions and had the diffs pegged by Rakeway. He got the job as Ashcrofts declined to peg a diff fitted with KAM r&P and when I visited Rakeway he seamed to know his stuff and the sample diff he had looked well done. He tightens up the pad until the pad just touches (diff gets stiff to turn), then backs off 1/4 turn. Only done AFC since, but work fine. Think it was £140 + vat per diff if I remeber right. The slipper pad is not retained onto the threaded pins.

Adrian

[smo]

I have never tried it, but my own thoughts on the matter are that a slipper pad may not be necessary. My thinking is that it is only under moments of extreme load that the crown wheel will be forced away from the pinion. If this is true, then I would have thought that even if the bolt ends were left 'bare', but set up VERY close to the crownwhweel, they would stop the flex and the contact between the crownwheel and the bolt ends would be momentary. Since there is plenty of oil being flung about, and the back of the crownwheel is smooth, they would do the job fine. I am assuming that there is room to fit at least one large diameter bolt which won't bend easily.

Regards,

Diff

If you were to fit just one large bolt, you could actually machine a cylindrical slipper which is threaded for the top, chamfer the top edge and voila, captive slipper pad, no possible damage from steel-on-steel contact and probably easier to setup than using a non-captive pad and 2 smaller bolts.

[Erwin]

@Jon White: how far are you with the diff. pegging?

What did you use to weld the plate on de diff?

I am trying to DIY. I will not be easy to drill the holes at the correct place.

[Bush65]

As the ratio changes from 3.54:1 to 4.11:1 to 4.75:1 the pinion diam/radius becomes smaller.

Simple mechanics tells us that, for the same input torque, as the diam/radius of the pinion reduces, the tangential force acting on the teeth increases.

Because the force (called the real tooth load) between mating teeth is at an angle (the pressure angle), for the tangential component of this force, there is a proportional radial force (called the tooth separation load).

Deflection of the components (pinion, crownwheel, carrier, etc) due to the tooth separation load, changes the location of the contact patch, adversely affecting the stress distribution in the mating teeth (which leads to tooth breakage).

So a 4.75:1 diff will have higher tooth loads, combined with greater deflection, to make them weaker than a 3.54:1 diff.

Pegging helps by limiting deflection of the crownwheel and carrier. Obviously the smaller the clearance between the slipper pad and the CW the better.

Larger teeth are stronger than smaller teeth, so a 4.1:1 CWP with 41 teeth on CW and 10 teeth on pinion will have (if all else is equal - material, heat treatment, precision etc) stronger teeth than a 4.11:1 CWP with 37 teeth on CW and 9 teeth on pinion.

[Jon White]

@Jon White: how far are you with the diff. pegging?

What did you use to weld the plate on de diff?

I am trying to DIY. I will not be easy to drill the holes at the correct place.

More or less done. Just having fun and games with stub shafts that dont want to fit together at the moment!

I got a mate to TIG weld it up for me.

Drilling is easy enough if you've a pillar drill and a decent clamp. You need to measure carefully and mark correctly to get he holes in the right place.

Jon

[Erwin]

You need to measure carefully and mark correctly to get he holes in the right place.

Jon

I did some practice on a old diff. and the first hole was wrong.

For the drilling that will be a problem because i dont have a big pillar drill.

Do you now the exact distance between the C&P? In the rrc manual the say 0,1 mm and the 0,19 mm but some people say 0,25mm.

[Jon White]

There is no correct distance - you need to adjust the clearance until you get the correct amount of backlash.

Jon

[Erwin]

And how do i find out the correct amount of backlash?

Is there a faq or topic?

I am not removing the pinion so normal that will be no problem.

[Jon White]

You will need to remove the pinion otherwise the bearing will fill with swarf as you drill the casing!

If you have the genuine (non haynes) manual this covers setting the backlash of diffs. Available for free download in PDF format from various places on the net if you look hard enough!

I tend to just do them by feel, but I wouldnt recommend that if you've never done one before! I've become a bit of an expert at it now - I've blown 3 in 2 months!

Jon

Jon

[smo]

I tend to just do them by feel, but I wouldnt recommend that if you've never done one before! I've become a bit of an expert at it now - I've blown 3 in 2 months!

Jon

Aah but is that why they are blown, because you set them by feel?

[BogMonster]

Aah but is that why they are blown, because you set them by feel?

I have watched people do it by feel, check what the backlash feels like before you start and aim for the same when it is all back together. Generally the idea seems to be to aim for an amount of backlash that is as small as it can be, but so you can still "just" feel backlash, if you see what I mean, and then rotate the diff quite a few times to check there are no tight spots. I have been wondering about trying to re-set the diffs in my 90 on the basis that they are clanky slack cr*p things!

[Jon White]

Spot on - I've tried measuring it with a dial gauage etc and got the hump with it! I do it the way stephen describes - I usually set it up so that there is zero backlash at all, but such that it doesnt bind anywhere when rotated. Then back off a little at a time until there is the tiniest bit of backlash in it that you can feel.

IIRC the manual says it should be something like 4 thou of backlash, which frankly is barely detectable!

I've watched a friend who is a proffessional do this and I do them the same way as he showed me. He rebuilt the last 2 I blew, so you cant blame me for them blowing up!

Problem is I'm running series diffs with ARB's and big tyres - they're not generally regarded as the strongest!

Jon

[Erwin]

You will need to remove the pinion otherwise the bearing will fill with swarf as you drill the casing!

Did not do that but now i see why. I will remove the pinion to clean the bearing.

I tend to just do them by feel, but I wouldnt recommend that if you've never done one before! I've become a bit of an expert at it now - I've blown 3 in 2 months!

I did al the diffs of my RRC by feeling (like they told here) no problems for several years.

I did the rear diff to, still no problem but the front keeps breaking the crownwheel (5 yet).

Here are some pictures from my diff.

I will cut the bolts later to the proper length and make a sleeve in it.

[Tonk]

theres nothing wrong with setting a diff up by feel, i've built errrrr quite a few that way

Erwin, thats a horrible looking weld, need to start with cleaning the diff casing more and turn your welder up by the looks of it to me. you'll get a better result if you tig it next time

dont forget to put your locknuts on aswell