Diff pinion drive flanges

[Snagger]

Hi all.

I have just stripped a standard  24spline rear diff from a late Discovery 1.  It had the three hole Rotoflex flange with pig to remove central spigot.  I was given two other 24 spline diff centres, one with crown gear and pinion, for free by the chap who sold me the first diff (all in excellent condition and a great deal for £40!).

The spare pinion had a loosely fitted square headed flange, which I had planned to use on the rebuilt unit until I found a wear grove from the seal.  But it is 1/2” shorter than the three bolt flange that came off.  A replacement is on the way.  But I have a question about that flange type.

I found there are mostly short flanges available, and also spacer rings that would make up the distance.  I did find round flanges with longer necks and a plain internally section for the inner end which look similar in proportion and style to the long three hole flange I took off.

The question is, are the shorter flanges a short-nosed diff part that can be used on long-nosed diffs with the spacer, or were the spacer and shorter flange introduced to reduce costs because the spacer would likely never need replacing, reducing the scrapped material on flange replacements (the long and short flange kits are the same price anyway)?

A related question: I bought a bearing and seal kit from Ashcroft, so have the four bearings but two seals.  The both appear to have the same diameter DS, but one is much thinner than the other.  Is this also to accommodate the long and short nosed diff types?

[missingsid]

I think a chat with Nige HfH is in order.

[Will@LRW]

The square faced, shorter flange with the spacer is the earlier style. The longer one with the round face is a later style. The short nose and long nose have different flanges regardless. Whether their lengths are similar, I don't know off hand.

Additionally, there are two styles of seal for the long nose diff which match to the mudshield and not the flange. The thinner style is the later one.

I wrote a guide with pictures that may help: https://www.lrworkshop.com/axles-differentials/pinion-flange-pinion-oil-seals

[Hybrid_From_Hell]

If you wnat to fit a 24 spline unit then there are 2 x choices

 

FRC3002 - short and will require a spacer

STC4858 - which is a like for like swap for the 3 bolt D2 version

 

BOTH of these will leave a gap between the prop and the flange and you really require a 200 TDi rear prop to finish things off or buy / make a spacer

Use FTC5258 as a pinion seal for either of the above

Nige

[Snagger]

Thanks, guys.

So, basically it’s best to use the later deep flange, the deep mud shield and the thin seal (that accommodates the later shield)…. Good stuff.  That is a very detailed page, Will!

 

Thanks for the warning about prop shafts, Nige.  This is being built up with an Ashcroft ATB and the 4.1:1 gear set you sold me in the summer to eventually fit to the 109 (Discovery axle).  For now it’s just a project I can work on out here, but I’ll be using the Ashcroft 23-24 spline shafts that you advised me on.  Your video on the differing shaft types was very useful.  Also worrying - I’d like to fit ATBs to my RRC when I get to continue its rebuild, and those front shafts look awfully weak at the CV end.  It’s going to get expensive.

[Snagger]

Well, some progress.

I built up the the ATB with the 4.1 gear set and 5mm spacer ring from Ashcroft Transmissions and installed it with new bearings in the housing.  Steering up the pinion is a bit of a faff if you don’t have all the tools, good workbench and a vice - working on a nylon cutting board on the floor or kitchen worktop isn’t ideal, and measuring pinion depth with a straight edge across the bearing cap faces and a digital calliper is fiddly, but I got a reading with care and patience of only 0.05mm of the figure engraved (not stamped) in the end of the pinion head.  That was using the original shim installed in the casing (which was a 3.54 unit).  I thought that was probably close enough, given the limitations of my measuring methods, to continue assembly towards mesh checking.

The spacer ring needed a little filing down around the edge and by som bolt holes, having a few slight high spots.  It’s sheet steel and hasn’t been faced on a machine, and I measured a slight variation in thickness across it.  I’m waiting for a dial indicator to arrive to check the assembled unit for runout, but from basic attempts to check it with the calliper (not easy), I got consistent results measures at every 60 degrees of rotation of three consecutive identical readings, two adjacent 0.05mm higher and then one 0.04mm lower than the three “datum” readings.  I need to check with the DTI, obviously, but I have a suspicion the spacer ring is the cause.  I’ll strip the parts again, run the diff centre by itself and check for any runout on the ring mating face, marking any high spot, then check the spacer again and if I do find a thin side as before, set that against the diff high spot to even it out.  
 

Setting the pinion bearing preload was a surprise to me.  Time consuming, but otherwise simple (made slightly harder by the mud shield on the new pinion flange being slightly crooked and binding on the casing nose).  I was surprised at how tight they have to be - being new bearings, I set the preload to just under 25 inch-pounds.  The effort to turn the pinion by hand is more than I’d have expected to be needed.

I tried the mesh after setting about 0.1mm backlash and ran a pattern (pics 1 and 2 below).  The marks were very close to the toe on both sides, so I increased the backlash.  

I’m guessing without the DTI, but I estimate it’s around 0.2mm now, which is a lot, but the pattern was better (3 and 4 below) Somewhere between 1/4-1/3 from the toe on the drive side, still closer on the coast side.  So, it looks like the pinion shim is close to where it needs to be and should need only fine refinement once I can be sure of the runout.

[Gazzar]

That's great work. I've never played with diffs, looks fun.

 

[Snagger]

57 minutes ago, Gazzar said:

That's great work. I've never played with diffs, looks fun.

 

It’s time consuming and some of it is heavy work, especially without a tool to hold the pinion still while undoing its nut or having the correct tool for the side nuts.  Using the calliper for measuring has been very fiddly, but I got my DTI now.  But it’s interesting trying something new, which was the point of the project rather than having Nige or Ashcroft build it for me, and I think I’ll be able to do it correctly even with my limited facilities.  It’ll just take me a lot longer than it’d take them.  Hopefully I won’t break and bones or lose any fingers in the process. 😜

I can’t find Prussian Blue locally, so I used some oil paint, which seems to work adequately, if not as well, and seems better than the yellow paste the Yanks use for the purpose.

Anyway, my daughter gets here tonight at midnight, my son hopefully about 24 hours later than that, and few hours after I have to go on a trip.  I know what I’m getting for Christmas - a 16 hour flight and 19 hour duty!  😆. The diff will have to wait until I’m back; the kitchen is needed for other tasks!

[ashtrans]

is it our ring and pinion ?

are you sure you should be using the spacer ring ?

Dave

[Snagger]

No Dave, I bought the used ring and pinion (4.1:1) from Hybrid From Hell (forum member and mod, Xcess 4x4 owner).  He inspected it before sale and said it was in good order.  Looks good to me, but I don’t have any experience in close inspection of these things, just cursory checks for corrosion, chips and burrs.  Nige couldn’t determine who made it.  I assumed it was quite old, having a nut and split pin on the pinion, but that transpires to be M22, so it’s newer than I suspected. 
 

The pinion head is approximately 5mm smaller diameter than the 3.54:1 head that came out and the ring gear is about 2mm shallower, so that makes about 4.5mm smaller space between the pinion axis and the flat face of the ring gear.  Since your spacer is 5mm, it seemed to cry out for it.  I haven’t even tried assembling the unit without the spacer, though there is no reason I couldn’t - I tightened all the bolts pretty hard for mesh testing, but not to the full specs and haven’t used thread lock yet.  This was just a very rough and ready first go to see if I could get a pattern for the pinion depth while I waited to get the DTI to do the backlash and runout checks properly.  I’m not concerned about anything at all yet!

Any news on the Salisbury version?  I’ll be after one of those for this vehicle’s back end!  I had to get gears for that on the cheap too - I got a good used Dana 60 set with 10 spline pinion.  I’m less certain about those fitting the axle than these gears, though…

[Gazzar]

I'm guessing it's a Santana diff, or perhaps an Iranian copy?

[Gazzar]

I'll try find my Santana diffs, and look at the thread. I'm not opening it up, though.

[ashtrans]

A fine pitched M22 on the pinion is likely to be a KAM one, I was just concerned it was one of ours and you were using the spacer which wouldn’t be required,

I don’t know if the KAM ones used spacers but if it’s built up OK and both side adjuster nuts are sitting OK then that’s fine.

Salisbury ATB’s are late Jan / early Feb

Dave

[Snagger]

Brilliant!

 

Thanks for the thought about the spacer, Dave.  The M22 is 1.5mm pitch.  I’d be happy if it’s KAM, though I suspect Nige would have recognised it as such as he’s familiar with their stuff.  As long as it works, though…

[Snagger]

I had a bit of a play about today.  I stripped the ring gear off and measured the diff flange runout and spacer ring thickness variations.  The diff had total variations of 0.02mm and the spacer 0.03 mm, so pretty good.  The high and low spots on the diff flange were about 150degrees apart.  By remarkable coincidence, thick and thin spots of the spacer ring matched fairly closely, so the combined variations should be about 0.01mm.  With those configured, I refit the ring gear with thread lock on the bolts, so that is one element complete.

Another go at running a pattern suggested the pinion was too high, with the contact patches too close to the toe on both sides of the teeth.  I removed the shim, fit one 0.3mm thinner, reset the pinion preload and then ran another pattern.  This time, I think the pattern on the coast side looks good, but the drive side is looking like the pinion is low.  I did read a set of instructions for fitting Yukon gear sets that said to prioritise the coast side pattern when setting up used gears, which makes sense as they’d be less worn.  I have the time, so I’ll be trying another shim setting between where I started from and where it is now to try for a more balanced pattern.

[Snagger]

I refit the original shim, reset the backlash and had a few tries within the backlash range of 0.1-0.17mm and got this at 0.13mm.  I think it looks right.  
 

The pinion depth looks good to me, with the contact well placed between the root and the face of the teeth.  I remember KAM had written on their website that the manufacturing tolerances have more to do with the casing than the gears or bearings, and that the original shim is correct in 95% of instances when replacing the gear set, even when changing ratios (their percentage, not mine).  I successfully applied that principle to swapping diff and pinion from a 110 axle into a 109, and later, the 109 pinion and diff into a 110 axle.  More notably, the original shim from the casing resulted in the pinion head being 76.25mm below the mean bearing cap mating, just as engraved into the pinion head, within +/- 0.02mm.  So I’m confident that I can fit the new outer race in place of the old one which had its outer face shaved to make it easy to fit and remove for setting up the shim.

I am a little less sure about the backlash, because the coast side pattern at first glance looks very toe biased, but a closer look seems to me to show a decent patch less polished, the bright metal near the toe just being more cleaned off.  I’d value second opinions on that, though.  The drive side looks like it is roughly where it should be, centred around 1/3 of the way from the toe.  
 

It is amazing how much contradictory information is out there for something like this.  The LR manuals only show the drive side of the gears and don’t mention the coast side.  Yukon’s instructions say to concentrate on the coast side when setting up used gears.  Some seem to say that if the pattern on the drive and coast side show similar contact points close to the toe, increase backlash and close to the heel decrease backlash, but others say that is a pinion issue.  It’s a minefield.  I think some of it depends on whether or not the gears are hypoid, ie. the two rotational axis are offset (like the Salisbury).

 

[Snagger]

This doesn’t help either - the LR manual talks about toe and heel contact for diagrams D and E, but mixes them up; D says heel but shows heel contact on the diagram, and E does the opposite.  So, do you ignore the diagrams and follow the instruction for the written condition statement, or do you do the action written for the labelled picture and ignore the condition statement?  As far as the overwhelming bulk of other guides say, you have to ignore their condition statements and match the diagram and actions letters, ie heel contact is too much backlash and toe contact from too little.  

[Snagger]

Done.

I repainted the housing, installed the new pinion front outer race with the original shim, sorted out the mud shield contact with a little percussive engineering, reset the preload, fitted the seal, lathered everything up generously with LM grease, installed the diff unit for the last time, set the backlash (got slightly different positions on the adjuster nuts for some reason, so ended up with the minimum 0.10 backlash instead of the 0.13 I got last night, perhaps because of the lubrication), and ran another contact pattern in three positions before tapping in the locking pins on the main bearing caps.

The final contact pattern was ideal for pinion depth, has almost full contact on the coast (concave) side with just a bit untouched at each end, and a good toe pattern on the drive (convex) side with only the last 15-20% to the heel not showing strong contact.  I think that is as good as I’m going to get with used gears and the limited accuracy I can achieve with the pinion depth (no setting block and no details on required depth for the head other than the engraved depth relative to the bearing cap faces from another housing, which may have notable tolerance variations).

The final job was to touch up the rim of the housing where it had been scuffed while torquing down the pinion and bearing caps, apply copious amounts of grease to the diff side gear splines and spray the gears, bearing caps and drive flange down heavily with WD40 and wrap it all tightly in clingfilm to keep the moisture out while it sits in storage.

While I was clearing up, I took a close look at the bits I got at the same time as the complete used Discovery final drive unit, which consisted of another diff, ring and pinion, a ring less diff and several fixings.  The ringless diff is in very good condition indeed, no marks on the teeth and no play on them, just smooth rotation.  The diff that came out of the housing I used was generally good and just needs new shims for the spider gears.  The third diff had a few broken teeth on the spider gears and a fair bit of play on all four, so went in the bin along with the loose main bearing caps (no matched housing to fit them to, so they’re scrap) and some lightly rusting bearings.  The rings and pinions have been sprayed heavily in WD40 and bagged in freezer bags with as much air removed as possible for retention as spares for the RRC.  The good diffs will be offered for anyone local to collect for free, otherwise they’ll sit in storage with the oil they have on them and will likely come back to the UK in the future, but I still intend to fit ATBs, not these, to the RR.  The next project may be the Fairey overdrive I bought through Gazzar.

[Anderzander]

Gosh - I missed this, and super pertinent for me. I’ve just pulled a failed diff that had an Ashcroft ATB thrown in. I’m planning to rebuild it and learn as I go. 

Looks like you’re doing a great job. 

Did you ream out an old set of bearings to make swapping the thrust washers in and out? 
 

[Snagger]

Yes, basically, though it is only a matter of reducing the outer diameter of the front pinion bearing outer race.  I also did the same to the rear outer race so I could also use them as drifts for inserting the new races and the seal.

 

 For setting up, I fit the new front inner race to the pinion, the new rear outer race to the housing and used the new rear inner on the pinion for testing as it slides on and off the pinion quite easily.  The only bits that needs a lot removing to change shims are that front outer and rear inner - the front inner and rear outer have no shims so can be installed straight away.

Trailfitters tool box on YouTube is useful.

Figures you’ll need: 

Pinion nut or bolt torque 95’lb

Pinion preload (once depth is set and using small shims to space rear bearing) 15 INCH lbs for old bearings, 20-25 for new

Main bearing cap bolts 65 ‘lbs

Ring gear bolts 45’lbs

Backlash 0.1-0.17mm

 

Other useful nuggets are to set pinion depth, existing shims are probably correct even if changing gear sets, but you have to check.  With the shim in place and preload set (by bolt tension, rear shims not necessary until final main shim is determined), look for a contact pattern in the middle between root and face.  Don’t worry about heel and toe until later.  Contact at the root means you need a thinner shim behind the front bearing outer race, contact near the face means you need a thicker shim.  Once that is set, to can set the backlash better to heel and toe patterns.  Make sure everything is torqued up properly when running patterns, not just tight on a ratchet.

[Gazzar]

Don't know if this warrants a new thread, but how compatible are Salisbury diffs with jaguar powerlok diffs?

[Snagger]

As far as I can see, the Jags use the Salisbury equivalent to the Dana44, but Land Rover use the equivalent to the Dana60, so the Jag unit would be too small.

[Gazzar]

I will be looking at this in detail soon, add I've finally obtained a true trac for my 109. The plan is to build up a spare diff and just swap out the exciting unit.