Nick's Land Rover - Series III Rebuild

I have just collected a 110 Salisbury rear axle to go with the Discovery 200Tdi front axle previously sourced for the axle upgrade.

The Discovery axle seems near mint, with almost no rust at all on the axle case and perfect swivel housings.  It has a small dent in the bottom of the diff pan which will need beating out, but since I plan on replacing the swivel seals as a precaution anyway, removing the diff to beat out the dent is little extra effort.  It will give me a chance to inspect the diff closely anyway.  Aside from that, the brakes need a full overhaul, including the replacement of the worn and heavily rusted discs and pads.  Hopefully, the callipers will not need anything other than thorough cleaning and painting.

The Salisbury axle, being far older, is rustier.  Its suspension brackets are all rusted through, but that is of no consequence as they all have to be removed anyway.  The drum brakes would need overhaul, which could easily and cheaply be done by simply transferring the identical rear brakes from the 109’s current (original) rear Salisbury axle, but I’ll be modifying the axle to discs.  I have obtained the two calliper brackets (part number FTC3306) from PA Blanchard (military Land Rover specialist in Yorkshire), having found the parts to be listed as “NLA” – no longer available – from other sources, even (and unusually) including the ever-reliable Dunsfold Land Rover (one of my other favourite suppliers).  So, if you have a drum braked axle that you want to convert to discs, buy these brackets now before they’re all gone!  I have sourced, though not yet taken delivery of, a pair of hubs, callipers, discs and mud shields from a Discovery rear axle that is being broken, all of which should be a direct fit.  I believe that I will need to fit 6 or 7mm spacers between the axle’s end flanges and the new brackets to align the callipers with the discs, but that can simply be made of sheet steel (washers or tubes would allow the securing bolts to bend and fracture – the spacer needs to be one solid piece).

Of course, the existing coil-sprung suspension brackets all need to be removed from the casing and new leaf spring saddles need to be attached.  While on the rear axle this is a relatively simple task, setting standard dimension Series-like saddles parallel to the diff axis and retaining the new axle’s bump stop plates (a flat area in the casting of the diff housing on the right hand side of the 110 Salisbury), it is far more complex on the front axle.  This will require custom saddles to accommodate the shape of the diff housing, which sits slightly into the right hand saddle on these wider axles.  Furthermore, the saddles have to be taller in order for the aft mounted track rod to clear the top of the leaf springs.

I have been conducting a lot of research into this job, trying to find the simplest way of securing the front axle and setting up the steering.  From contacting numerous others who have already done the conversion, it is clear that I need to maintain the standard castor angle on the swivel pins in order to avoid excessively stable or unstable steering, so rotating the axle to move the track rod up or down is not an option.  The solution is to raise the whole axle, complete with steering gear, away from the tops of the springs. The only way of doing it is by having these taller saddles (photo courtesy of John Ralphs, BHCLRC) – using a LHD right hand swivel and fitting a front mounted track rod gives reversed Ackerman angles and doesn’t work, and severely modifying the track rod to fit around the springs would be weak and very dangerous.

One contact (Koos, Expeditionportal.com) has used saddles of 1″ height between the top of the spring and the lowest part of the axle tube and finds he has just enough clearance.  This is roughly twice the standard height of the stock Series saddles.  His is the best set up I have seen for this, but he has used a standard chassis with 1-ton shackles to regain some of the height lost from the tall saddles, which also rotates the rear of the spring down, increasing the track rod clearance for the standard castor angle.  He chose not to counter that effect when attaching his saddles, copying the angular relationship between saddle and swivel pins on the SIII axle to his his new RR axle in order to avoid prop shaft contact with his larger Toyota engine, resulting in him getting a 5 degree castor angle (standard is 3 degrees) and heavier steering.

Since I have 1-ton chassis and shackles already, I will be using the same saddle/swivel geometry as on a standard SIII axle.  I will try the same 1″ height as this fellow, adding a shim if I find the track rod to be too close.  Another contact (Meccano, LR4×4.com) has found that additional track rod clearance can be obtained by using a Land Rover 101 FC track rod, slightly shortened, with Range Rover drop arm linkage kits.  This rod is slightly kinked at each end, so the centre section is raised up over the springs and closer to the diff nose.  HD custom rods made to this pattern are already available, but at a cost of over £235 are a little excessive.  So, thanks to those twos pioneering efforts, near perfect execution and glad sharing of information, I know exactly what needs to be done without any trial and error.

The brakes will use standard discs and callipers all round, with the same EBC “Green Stuff” pads that have impressed me on my Range Rover Classic.  The hydraulic system will mimic the Range Rover and Discovery non-ABS system, rather than the Defender system, as that is what my callipers came from and what seems to have the greatest redundancy.  This means that the larger side of the master cylinder will power a piston-pair in each calliper, while the small side operates the secondary piston-pair in the front callipers only.  This will require an additional pair of flexible hoses at the front, just like on the RR and Discovery.  I already have the pressure reducing valve for the rear callipers from the donor Discovery.  I’m hoping that the existing SIII dual circuit master cylinder and servo will be up to the job, but I have heard anecdotally that it gives a heavy pedal.  If that is what transpires, I shall use the Discovery servo and master cylinder (from the same donor) mounted on the SIII pedal box.  This will require an 8mm shim/adaptor plate between the pedal box and servo and a small cut to the wing top to clear the servo.  I may just do this anyway, depending on how much time is available.

Originally cynical about using 3.54:1 diff ratios on a Series vehicle, I will now be retaining the new axles’ diffs.  This will give me far better motorway cruising and better fuel consumption (important for long trips and daily commuting) and should not be over geared behind the Tdi.  The only two flaws are the increase to low range, which could be awkward on very steep climbs and descents (apparently, the SII Suffix B transfer box has much lower low range gears, so this could be a future remedy if it’s problematic) and the need to recalibrate the speedometer/odometer (for which I’ll probably use speedycables.co.uk).  The overdrive would be used considerably less as a result, mainly when used as a splitter between third and fourth and as a cruising gear above 60mph.  This will reduce strain on the overdrive, prolonging its life, but also reduce temperatures of the shared oil in the transfer box and overdrive.  I am hoping for about 15% improvement in fuel economy form this 35% gearing increase.

This just leaves the issue of the steering.  The coil-sprung models’ axles have far greater steering lock than the Series axles, which raises the concern that the steering box will reach its limits before the swivels, exposing the steering box to far greater risk of damage/destruction when hitting stumps or potholes at full lock.  Happily, the swivel arm on the later axles is shorter than on the Series swivel, so the gearing is increased.  This means that the axle still reaches its locks before the Series steering box, and the amount of steering response from a given input is reduced.  On the flip-side, it also means the steering will become a little heavier.  Given that the steering on my 109 is already heavy because of the 7″ 8-spokes, the slightly wider 235 tyres (about 1.5″ wider tread than the standard 7.50s), the steering damper and the smaller steering wheel, this will be unacceptable (it’s just too hard to manoeuvre in tight spaces, though it is fine in normal car parks and on the road), so I will be fitting power assisted steering (PAS).  This will be covered by another article and is likely to be undertaken before the axle swap.  In a nutshell, Ill be using standard 200Tdi Defender parts in conjunction with a Range Rover P38 box.

Axles, Steering

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