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Discovery/Def/RR axles on to leaf springs


Snagger

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Hi everyone.

I have a 109 on 1-ton chassis and shackles with TIC HD parabolics. The braking system is the late dual circuit, servo assisted type. The dampers are Procomp ES9000s. The vehicle is used as a daily commuter and also for trips, with a high gross weight and relatively high CoG.

I'd like to fit later axles for a variety of reasons, principally better brakes, greater steering lock, CV jointed swivels and wider track. I have already secured a Discovery 200Tdi front axle in great condition, and plan to fit a Defender's disc braked rear Salisbury axle.

As far as I can see, the rear axle looks pretty simple, just needing the leaf spring seats welding on and either a bracket welded to the axle for the 109 damper configuration, or the use of the coiler's upper damper mounts bolted through new bolt holes (with spacer tubes) in the chassis rails (advice on which would be best would be appreciated).

The front axle looks far more complicated, with the issue of the diff housing being very close to the right side spring and clearance issues between the track rod and the springs and dampers. There is also the issue of setting the castor angle.

I have found one existing thread on here regarding the conversion, and it gave me a few ideas, but it's a long-dead thread and there was no follow up as to how well the vehicles were performing. I was wondering if anyone one could please give me advice on the following:

1) How do you set the castor angle accurately to the required 3 degrees?

2) Is it necessary to have thick spring seats, or can the correct castor angle and track rod clearance be achieved with relatively standard thickness seats?

3) Does fitting the dampers inverted to clear the track rod, as done on the black Air-portable (Mechano's?), cause any problems for the dampers, or do I need to fabricate brackets to mount the dampers above the track rod axis?

4) I was planning to use a TD5 Discovery front prop shaft so that the rear end would have a double-cardan joint - can this be done without much hassle?

5) Has anyone any ideas on how to fit the axle donor's anti-sway bars too, as the 109 suffers significant roll on corners, especially when heavily laden?

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1) How do you set the castor angle accurately to the required 3 degrees?

lots of measuring... if my memory serves me correct. there are machined faces on the swival that are 90 degrees to the swival pins. this makes an ideal point to stick a inclonometer!!!

2) Is it necessary to have thick spring seats, or can the correct castor angle and track rod clearance be achieved with relatively standard thickness seats?

If you intend to use standard shackles at the rear of the leaf spring you will need to have bigger seats to allow clearance... just noticed that your using 1-ton shackles. which means you dont need extended seats if set at a correct castor angle.

3) Does fitting the dampers inverted to clear the track rod, as done on the black Air-portable (Mechano's?), cause any problems for the dampers, or do I need to fabricate brackets to mount the dampers above the track rod axis?

The dampers were not flipped at all for extra clearance. Only for "anti water trap, rusting up my shocks" purposes

No you shouldn't really puttign them up side down... and it does make the shocks stiffer

4) I was planning to use a TD5 Discovery front prop shaft so that the rear end would have a double-cardan joint - can this be done without much hassle?

i dont honestly think you will need a double cardan joint.

5) Has anyone any ideas on how to fit the axle donor's anti-sway bars too, as the 109 suffers significant roll on corners, especially when heavily laden?

I dont see why it cant be done on the rear . if you can get hold of the mounting plinths... of fabricate some. It would probably fit! you would just have to ensure clearance of exhausts etc.

Although i dont think there would be enough room up front ?!?

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1) How do you set the castor angle accurately to the required 3 degrees?

lots of measuring... if my memory serves me correct. there are machined faces on the swival that are 90 degrees to the swival pins. this makes an ideal point to stick a inclonometer!!!

2) Is it necessary to have thick spring seats, or can the correct castor angle and track rod clearance be achieved with relatively standard thickness seats?

If you intend to use standard shackles at the rear of the leaf spring you will need to have bigger seats to allow clearance... just noticed that your using 1-ton shackles. which means you dont need extended seats if set at a correct castor angle.

3) Does fitting the dampers inverted to clear the track rod, as done on the black Air-portable (Mechano's?), cause any problems for the dampers, or do I need to fabricate brackets to mount the dampers above the track rod axis?

The dampers were not flipped at all for extra clearance. Only for "anti water trap, rusting up my shocks" purposes

No you shouldn't really puttign them up side down... and it does make the shocks stiffer

4) I was planning to use a TD5 Discovery front prop shaft so that the rear end would have a double-cardan joint - can this be done without much hassle?

i dont honestly think you will need a double cardan joint.

5) Has anyone any ideas on how to fit the axle donor's anti-sway bars too, as the 109 suffers significant roll on corners, especially when heavily laden?

I dont see why it cant be done on the rear . if you can get hold of the mounting plinths... of fabricate some. It would probably fit! you would just have to ensure clearance of exhausts etc.

Although i dont think there would be enough room up front ?!?

Thanks for that, and sorry for mis-spelling your log-on name!

My shackles are indeed 1-ton, but so are the dumbirons, so the current spring and axle axis are horizontal, just like with standard dumbirons and shackles. I don't really want to lose any suspension height if it can be avoided because the winch, bonnet spare wheel, steering guard, bull bar, pioneer tools and extensive sound proofing make the front very heavy and have already lowered the front end to a height comparable to when it was on the same springs with standard chassis and shackles without all the accessories. I suppose, if necessary, I could have some extra long shackles made to rotate the springs and gain track rod clearance, but I was hoping to keep things simple. Do you have any ideas where I could get a reasonably priced and sufficiently accurate inclinometer?

It sounds like good news regarding the dampers, if I understand you correctly that you didn't need them to be inverted for the track rod. Having seen the other solution of custom brackets above the rod line, I had just assumed that there was a clearance issue. So, do you think that the erect dampers will fit straight on to the standard SIII spring plates with no track rod problems? As for the rear dampers, would using the coil sprung mounting system be better at resisting body roll around corners, or would it only help momentarily as the turn started?

The idea of fitting a TD5 Disco prop was just because with the relatively high ride height, the UJs are deflected by about 15 degrees (a guesstimate, not measured angle), but it looks like once the axle is swapped the front UJ would be nearly straight while the rear retains the kink. I figured that a double-cardan joint would help a lot with vibration, especially when under load. I don't know how the length of the Disco prop compares to a SIII front prop, but I assumed that swapping the yolks with Series ones would be a fairly simple affair. No doubt I'll now learn that the UJs are a different size!

As far as the anti sway bars go, I had planned to make custom mountings for the rear chassis that would be bolted through the sides of the main rails (with crush tubes, naturally). The chassis brackets would have to extend down from the rails a little for the bar to clear the rear fuel tank, and would have to be flanged 90 degrees to the coil spring arrangement (ie. you'd be able to look through the bracket longitudinally instead of laterally) so that the left bracket could be wrapped around the exhaust, which runs along the underside of the chassis rail. I can't see any problems with that. The front is trickier, but I had hoped to mount the bar using brackets on the top of the dumbirons just like the military Series ambulances. The problem may be connecting the bar to the axle. From what I can understand, fitting an anti-sway bar at one end only gives some undesirable handling characteristics.

I'd love to hear your thoughts on any of that - it's always useful to have the expertise of someone who has already done what you have in mind.

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I hope this doesn't come up as a repeat of my last response, but that hasn't appeared since Meccano's reply.

The following is in response to his comments:

1) Does anyone know where I could get a suitable inclinometer for setting the castor angle, and have an idea on price?

2) I am using 1-yon shackles, but also 1-ton hangers at the front of each spring, so the springs sit relatively level from one end to the other. Do you think I'll need to make some extra long shackles to avoid deep spring seats?

3) So, the dampers will fit using the standard attachment points without fouling the track rod on full lock?

4) Using a Discovery TD5 front prop would prevent any vibration from the mismatch between the horizontal transmission axis and inclined diff - does anyone know if the lengths are similar and if the UJs are the same (allowing the yolks to be swapped to fit the earlier transmission and diff)?

5) I was planning to use the standard rear anti-sway bar from the Defender, using mounts which bolt to the sides of the chassis rails, wrapping around the exhaust on the left side. For the front, I was hoping to mount the anti-sway bar on top of the dumbirons, using SII/SIII MoD ambulance sway bar brackets, though this will mean I have to fiddle with the Tdi rad/intercooler assembly which is mounted there at present. I read somewhere that using one anti-sway bar by itself can lead to dodgy handling - is this correct?

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I hope this doesn't come up as a repeat of my last response, but that hasn't appeared since Meccano's reply.

The following is in response to his comments:

1) Does anyone know where I could get a suitable inclinometer for setting the castor angle, and have an idea on price?

2) I am using 1-yon shackles, but also 1-ton hangers at the front of each spring, so the springs sit relatively level from one end to the other. Do you think I'll need to make some extra long shackles to avoid deep spring seats?

3) So, the dampers will fit using the standard attachment points without fouling the track rod on full lock?

4) Using a Discovery TD5 front prop would prevent any vibration from the mismatch between the horizontal transmission axis and inclined diff - does anyone know if the lengths are similar and if the UJs are the same (allowing the yolks to be swapped to fit the earlier transmission and diff)?

5) I was planning to use the standard rear anti-sway bar from the Defender, using mounts which bolt to the sides of the chassis rails, wrapping around the exhaust on the left side. For the front, I was hoping to mount the anti-sway bar on top of the dumbirons, using SII/SIII MoD ambulance sway bar brackets, though this will mean I have to fiddle with the Tdi rad/intercooler assembly which is mounted there at present. I read somewhere that using one anti-sway bar by itself can lead to dodgy handling - is this correct?

Hello Snagger

Sorry my reply was quite abrupt, it wasn't written in "my time" :lol:

Apologies for misreading the bit about it being a 1-ton. That does present you with problems. Other than using super duper extended shackles like you say, the only way to get around the track rod issue with a correct castor angle is either extended blocks which understandably you want to avoid ( as does ever one) or Look into custom track rods. I don’t know if you have seen in the threads you have looked up, that I mentioned the profile of a TD5 defender track rod. I have no definitive feedback that it would work, but it might be something you can pursue?

The only thing I might suggest is that having shackles that long may cause issues with the leverage on the chassis bush as the leaf twists along its length during articulation.

As far as the shocks go, I believe people only relocate the mounts to increase the ground clearance. The lower mounts I used where actually those used on the rear of a swb. And seems to give enough clearance. (I must also add I have es9000 which are stiffer and a larger diameter than the regular 3000's)

I can't really help on anything else as my props are different as I have a 5spd and lt230.

As far as anti roll bars, no idea about dodgy handling. However I though early 110's only have them on the rear?

I'd be interest to know more about the use of them on the ambulances. Do you have any pictures?

Chris

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No problem, Chris - I appreciate your help!

I can see your concerns over having excessively long shackles. I'll see what castor I can get with standard height seats before shimming them.

I'm trying to include manual drawings of the ambulance anti-sway bar systems - forgive me if they don't load correctly:

Nick

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post-4758-1224181481.jpeg

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  • 11 years later...

Yes I did.  They transpired to be not much of an issue.

The track rod cleared the spring tops easily with the three degree castor with the minimum height saddles.  The height is set by the diff banjo contacting the inboard edge of the right spring, needing special shaping of the saddle side on its inboard face but the outboard face and both sides of the left saddle had a simple circular cut at the top to take the plain sections of the axle tube.

The saddles were a bit taller, but I can’t remember by how much. I regained that lost height by adding a third leaf to my parabolics, which were sitting fairly flat with all the weight of the extra bits on the car.  That also helped stiffen the springs for cornering - they were probably softer than they should have been for that weight on two leafs.

Other issues were the front UJ of the prop shaft contacting the 12J-200Tdi engine mounting under braking, which was resolved with an arched mounting (probably not an issue if you use standard SIII mounts, but that’ll be a problem for running 12J, 19J or Defender versions of the 200Tdi with its lower fuel pump, and a little prop vibration from the mismatch in UJ angles, which I’ll fix with a double cardan jointed prop from a Discovery 2.  You also need a special shaped U bolt made up for the inboard Sid elf the right spring, and will need to remove and reorintate the bump stops.

Disc brakes and a steering circle about 2/3 that of a 90 are very good enhancements, and adding P38 power steering made it even better.

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Yes. Absolutely.  The difference in turning circle makes life a huge amount easier.  The brakes aren’t such a big deal - a bit less maintenance, but I didn’t find I had to do a great deal with the original 109 brakes.

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I live with it, but have to say, day-to-day, a 109's turning-circle is a real pain. I like your approach, not seen yours, I'm tempted. Yet an LR is one of those vehicles; it takes very little to have it looking like my 8YO's found a 'Magic-ray' to have his R/C cars go lifesize.

One day... meantime, and I use mine as a van, I'll avoid some loading-bays.

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You can see mine on that signature link.  I didn’t do a great job of detailing the axle conversion, more how I did the rear disc conversion.  But the PAS conversion was well documented, and that means I can use all the steering lock while stationary.  Parking and negotiating awkward places is dead easy now.  They’re two of the best transformations for ease and driving pleasure of the many mods on the vehicle.

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On 6/8/2020 at 12:58 PM, Snagger said:

Yes I did.  They transpired to be not much of an issue.

The track rod cleared the spring tops easily with the three degree castor with the minimum height saddles.  The height is set by the diff banjo contacting the inboard edge of the right spring, needing special shaping of the saddle side on its inboard face but the outboard face and both sides of the left saddle had a simple circular cut at the top to take the plain sections of the axle tube.

The saddles were a bit taller, but I can’t remember by how much. I regained that lost height by adding a third leaf to my parabolics, which were sitting fairly flat with all the weight of the extra bits on the car.  That also helped stiffen the springs for cornering - they were probably softer than they should have been for that weight on two leafs.

Other issues were the front UJ of the prop shaft contacting the 12J-200Tdi engine mounting under braking, which was resolved with an arched mounting (probably not an issue if you use standard SIII mounts, but that’ll be a problem for running 12J, 19J or Defender versions of the 200Tdi with its lower fuel pump, and a little prop vibration from the mismatch in UJ angles, which I’ll fix with a double cardan jointed prop from a Discovery 2.  You also need a special shaped U bolt made up for the inboard Sid elf the right spring, and will need to remove and reorintate the bump stops.

Disc brakes and a steering circle about 2/3 that of a 90 are very good enhancements, and adding P38 power steering made it even better.

Great information snagger, thank you. When you refer to minimum height saddles, do you mean you managed to clear the track rod when using standard shackles and not 1 ton shackles?

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The shackles were immaterial as I have matched chassis and shackles.  The geometry would be the same with a standard chassis and standard shackles.  However, that would lead a smaller than standard gap between bump stops, so would limit axle articulation off road as the saddles and bump stops on the axle are both taller due to the position of the diff and how the flare of the axle case sits over the spring.

You can add longer shackles with the standard chassis and this will mitigate some of the vehicle height loss and articulation loss.  Just make sure to account for it before welding the saddles to the axle and make sure the bump stops are correctly orientated to the rubber blocks, no longer parallel to the saddles.

Neither installation (standard spring inclination or inclines with longer shackles) will affect track rod clearance if you use a Defender (plain) track rod instead of the Discovery type.  You can use the adjustable section of the Discovery track rod to extend the Series drag link, as Defender drag links have a different end for the PAS box arm.  The minimum height of the saddles is determined by the flare of the diff housing over the right spring, so the saddle was notched to accommodate the diff with the casing being flush with the inboard edge of the saddle’s spring face, ie. the casing itself is touching the spring at that spot.

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