Diff pegging and locker install, Puma 130

[POD]

I've had Ashcroft airlocker, CV,s axles, flanges and pegging kit sitting in the shed for a couple of months, I planned to install lockers both ends when I bought the 130 and decided to increase the strength of the drivetrain whilst I was at it rather than do half a job and risk breaking the stock components. Fitting the rear axles and flanges is a quick job, but I needed to be able to have the vehicle off the road for the best part of a week before tackling the front end. I finally got time last week to put the 130 on stands for a few days and get the upgrade happening. Thought I would post it up for the sake of anyone else considering this modification, particularly of the pegging (after all, if you've seen one CV and axle, you've seen them all).

I stripped the diff down, then ground the edges of the pegging plates to sit nice and flush. I cleaned up the housing where the welding would take place by light use of a die grinder, then tacked the plates in position.
I then pre-heated the housing in an old LP gas oven (one of those things my wife has wanted me to get rid of for ages, I knew it would come in handy one day...).
I baked the diff on medium heat until crispy, while I cleaned up the swivel housings and stuff.

Ashcroft's website advocates use of TIG and Arc welding; as I don't have a TIG, I used my 195 amp MIG for the first part of the welding, then the arc welder for the main plate. Yes, I often keep a spare pair of jocks handy on such occasions.



I used Omega EN199 2.6mm electrodes for welding the main plate, a specialist cast-iron welding rod, 99% nickel. They have a very different feel from the 12P and 16TC electrodes I generally use. I found that I needed to keep the arc quite a bit longer than normal, they then flowed nicely. This also keeps a pretty hot arc, penetration looked to be good. As my arc welder is only capable of 140 amps, I used the thinner 2.6mm electrodes at full power, these welds used less than 2 rods (I bought 2 packs of 6 electrodes 'just in case', I can do a good deal on an unopened pack...)
After welding was complete, the housing went back into the oven for post-heating whilst I swapped the crownwheel from the old diff onto the locker and did some more cleaning up. That was enough for the day so I left the housing in the oven overnight after turning the gas off, to let it cool gradually.

Marking out the location of the pegging holes was a challenge due to the location of the holes in relation to the flange of the diff housing, which is the reference point. I used an awkward combination of square, straight-edge and vernier calipers. It didn't occur to me until later, that a simple carpenter's marking gauge with an elongated scribing needle would have been much more effective.
The housing was then mounted in the drill press, clamped down to the table as close to square as I could make it. A milling machine with a large angle plate would be much better suited to this part of the job.






I did the first hole completely, including a shallow counterbore and starting the tap, before moving the housing for the other hole. The purpose of the counterbore was to make sure the seating surface for the pegging nut was perpendicular to the hole. A small centre mounted in the drill chuck (a bit hard to see in the photo) is an effective way of starting a thread nice and square; it engages the centre hole in the back end of the tap.




Over to the vice to drill and tap the hole for the airline while the diff is still disassembled




Then the housing was given a thorough wash to ensure all the swarf was out prior to reinstalling the pinion and new seal.
As I was re-using the same pinion bearings, I didn't have to worry about setting the pinion height, just as well as I don't have the necessary special tool. The Ashcroft diff comes complete with new carrier bearings already installed, which is a nice touch.


This is what the pegging business looks like inside the diff housing; it has to be put in place prior to mounting the diff centre. Or you can do what I did and install the diff centre, set up the backlash and carrier preload, check the tooth pattern with bearing blue and THEN find that the pegging plate needs to go in first (that's why the pinion teeth already have blue on them).





I checked the crownwheel runout with a dial indicator, it was approximately .0004".
This photo also shows where the diff centre has been turned down to a reduced diameter to allow the pegging pad to support the back of the crownwheel.




Backlash was set to .005" which is what it was measured at prior to dismantling. The contact pattern was checked with bearing blue (sorry those photos didn't come out well), a little too close to the toe. Re-set the backlash to .008" which resulted in a nice pattern both sides of the teeth. No face - flank misalignment so thankfully no need to mess with the pinion depth.




I had a bit of an issue when it came to setting the clearance for the pegging pad. I could not get the diff to turn freely unless I backed the pegging setscrews out at least a full turn prior to tightening the locknuts (should be 1/4 turn for running clearance). A little investigation with the bearing blue revealed that the bronze pegging plate was rubbing on the radius of the carrier flange, the area that is turned down to a reduced diameter to accommodate the pegging modification. This meant that I had to remove some material from the edge of the bronze pad to provide clearance. I had to remove the diff centre again to rectify this, in fact it took me about 4 goes, taking a little off the bronze pad and setting the diff up all over again each time, to get a satisfactory result. I'm pretty sure this problem was due to the inherent inaccuracy of manually marking out the hole locations and then jigging the housing in the drill press to get the holes square. I think anyone else considering this mod should use a milling machine for this part of the job if at all possible.

I sealed the thread on the pegging bolts with loctite thread sealant, so hopefully there won't be any diff oil escaping around those threads. I hate oil leaks.












The air line was plumbed in to complete this part of the job. Tested the locker with compressed air and no leaks.



I didn't take any photos of the rest of the job, my hands were too greasy for much of it and fitting one CV joint is much like fitting another, after all. I can say that the Ashcroft bits are all beautifully machined and have a nice looking finish.

I contemplated slotting the swivel housings for a possible future suspension lift whilst I had them off, but decided against it; they would have to come off later to be rotated anyway, and I will take the time to set up a jig in the lathe to do this when the time comes, rather than using the drill press as I did with my previous vehicle. I also decided to renew all the internal seals and keep the CVs and wheel bearings lubed with grease (Dave Ashcroft, in response to an email enquiry, recommended grease over oil for the CVs), which suits me just fine as I have had more than enough vehicles with oil dribbling out of the swivel housings. I did ditch the spacer between the inner & outer wheel bearings and installed 2 nuts with lock tab as in earlier models. Only reason I can see for the one-nut-and-spacer setup is to save having to set the wheel bearing preload manually at the factory. The only other change I made was to screw the steering stops in a couple of extra turns and this has made an appreciable improvement to turning circle.


The entire job took about 22 hours over 3 and a half days, the time taken to ensure pre-heating and post-heating the diff housing meant it couldn't be rushed. Ashcroft's website makes no reference to heating the housing but all the research I did, including expert advice from Aulro members, indicated it is good practice when welding on castings.




I still have to remove the rear diff (again) to chase an air leak in the ARB locker; I bought a second pegging kit to do the rear diff when I was getting all the other bits (the same pegging kit for the Rover diff is used for the p38 diff in the rear of the Puma defender), however I'm still undecided as to whether I will go ahead and do the pegging mod again, as stated earlier I think this job ideally needs a milling machine to avoid the hassles I had due to the holes being either not located precisely enough or not perfectly square to the housing. Pegging an existing diff also requires complete disassembly of the diff centre in order to turn the flange down to the required diameter without filling the diff with chips, so all in all probably a 3 day job again.

[Old Rangie]

God only knows why Land Rover went down the thinner crown wheel idea in the short pinion diff.

I pulled my banjo rear axle out of the 130 when I did a wheel brg and white metal went right through everything, replacing whole assy with salisbury as per factory spec.

However as I travel around I have met a number of other ex Telstra Falcon Engineering 130's and all have the later banjo and short pinion diff. One explanation was that they (Telstra) changed the axle assy and fitted banjo with considerable beaming stiffening added for the purpose of strengthening the landing gear, not just the suspension!

When I first heard of this I thought this ridiculous but after traveling on roads Telstra employees would have used I start to see what was meant.

I am surprised they did not have the crown wheel pegged as well given all the weight they carried. I suppose cost.

Old Rangie.

[rick130]

God only knows why Land Rover went down the thinner crown wheel idea in the short pinion diff.

I pulled my banjo rear axle out of the 130 when I did a wheel brg and white metal went right through everything, replacing whole assy with salisbury as per factory spec.

However as I travel around I have met a number of other ex Telstra Falcon Engineering 130's and all have the later banjo and short pinion diff. One explanation was that they (Telstra) changed the axle assy and fitted banjo with considerable beaming stiffening added for the purpose of strengthening the landing gear, not just the suspension!

When I first heard of this I thought this ridiculous but after traveling on roads Telstra employees would have used I start to see what was meant.

I am surprised they did not have the crown wheel pegged as well given all the weight they carried. I suppose cost.

Old Rangie.

Grossly overloaded 130's driven at warp 5 over rather indifferent roads was resulting in some Telstra utes pulling the axle tubes out of the Sals assemblies.
The 'fix' was to replace the entire rear end with the UK Army 'Wolf' axle housing assemblies, hence the heavily braced rear end.