90/ discovery front axle swapping

MrF · Jun 9, 2023

Looking for some input on something I'm trying to do.
Backstory, I have a 90 that I've owned for 20 years that I'm finally rebuilding with a new chassis that I'm waiting for shipping notification hopefully today and because I have to replace brake lines/steering box etc while I'm doing this, I'm doing a lhd + 200tdi swap as its a approved engine type for this year here, and my 19j is done, 150k miles + a turbo runaway at 130k.

I've sourced that mythical creature, a reasonably priced extremely rotten discovery1 and its given up its components for this project, but when it comes to the front axle I have a issue in that I want to stay on the 90 rear axle with drums because a disc braked rear axle is too new for this vehicle (1990) and it might get checked on inspection. There's nothing wrong with my original 90 front axle apart from the challice balls aren't perfect and it has rhd hub castings.

So I could swap to the discovery front axle, and I read about the location arms being wider and I still have them from the donor disco. But it has the RR/Discovery dual circuit front calipers. Again because of eagle eyed inspectors I cant just run two brake hoses and a tee piece or loop the two ports because it'll be obvious I swapped in a disco front axle to someone who knows their stuff and I'm trying to be discreet.

So what are my options?
1) can I rebuild the 90 axle with just the lhd modified casting from the disco axle? Im thinking this is a no because the 90 axle is the older ralco top bush pivot setup and the discovery will be dual taper bearing pivots, but someone probably has experience having tried the same.

2) can I rebuild this discovery1 axle with the brakes from my 90 and keep the year correct unvented solid front discs setup. They've been good enough for 20 years, so not sure I need the improved power of vented brakes.

3) if 1 and 2 are not recommended, can I pick up a pair of defender front calipers from a early vented disc model & just bolt these on (and try to blag them as factory substitute parts). What about piston diameter and master cylinder bore sizes when remembering I have to keep the drum rear end?

So any experienced based answers to the above? I'm not scared of the work, but I want to keep it at the parts swapping level rather than fabrication.

Dr Strangeglove · Jun 9, 2023

I refurbished my front axle last year and I will give you notes from my swap.

Mine was a 10 spline axle, so I believe a 200 tdi. My original upgrade was change the swivel chalice and bits. The swivel axle case required the Railko bush type. I changed my front brakes to vented as I got them at a good price (or I would have stayed with standard). They were a straight forward swap apart from the bolts holding the caliper to the swivel housing - the earlier swivel housing (Railko type) uses a course thread - the later bearing type, which I believe is 300tdi, uses a fine thread.

My internals were OK so my drive shafts, CVs, diff, etc all were reused.

Later on I changed the axle case to a 300tdi unit.. This required that I also changed the "hockey sticks" as they are about 5mm wider, so remember this if you are buying bushes.

I can't comment on the LHD/RHD differences.

If you are doing a semi refurbishment, as I did, think about if you want to get new fixings so you can get them at the same time. This includes drive flanges, disk to hub, swivel ball to axle, hockey stick to axle bolts, brake caliper to swivel housing, plus associated gaskets etc. If using old bolts don't forget the threadlock.

I am sure others will be along shortly with further hints and tips.

Good luck.

Mick

Anaconda · Jun 9, 2023

My son has a Ninety with an early Disco 1 axle and it has solid discs which I presume are the ones original to his Ninety as it has single line brake calipers. The stub axle and hub are the Disco 1 units, I wonder if it just a matter of swapping the calipers to single brake line?
Stops well when the rear drums are adjusted properly.

MrF · Jun 9, 2023

Thanks for those responses, the lhd and rhd axles between a identical year/model differ only in the swivel housing casting, as the steering lugs are handed. On one of atlantic british youtube video's about converting to lhd he mentions using the casting from the discovery on the 90 when converting, but irrc it was a later 90 than mine so unsure its the same case.
I didn't realize the discovery1 still used a railco bush top pivot, but after the previous post mentioned it I looked up part numbers for the two vehicles and they are a different part number for the bush on the 90 and for the discovery1/RR, so I'm still erring on the side of point 1 being not possible.

But... I realized I hadn't inspected the donor discovery1 properly and had made some assumptions from appearances and discussions, and on checking it has unvented solid discs (with dual circuit calipers) and seems to use LR017951 as the part number for the discs same as my 90.
Hopefully I can just reuse my original 90 calipers + mounting bolts on this complete axle and be done after checking condition after cleanup, and of course ordering bushes to suit the discovery hockey sticks/trailing arms (sods law I've already ordered a complete bolt/bushing kit for the 90 as part of the re-chassis).

Dr Strangeglove · Jun 9, 2023

MrFluffy said:
Thanks for those responses, the lhd and rhd axles between a identical year/model differ only in the swivel housing casting, as the steering lugs are handed. On one of atlantic british youtube video's about converting to lhd he mentions using the casting from the discovery on the 90 when converting, but irrc it was a later 90 than mine so unsure its the same case.
I didn't realize the discovery1 still used a railco bush top pivot, but after the previous post mentioned it I looked up part numbers for the two vehicles and they are a different part number for the bush on the 90 and for the discovery1/RR, so I'm still erring on the side of point 1 being not possible.

But... I realized I hadn't inspected the donor discovery1 properly and had made some assumptions from appearances and discussions, and on checking it has unvented solid discs (with dual circuit calipers) and seems to use LR017951 as the part number for the discs same as my 90.
Hopefully I can just reuse my original 90 calipers + mounting bolts on this complete axle and be done after checking condition after cleanup, and of course ordering bushes to suit the discovery hockey sticks/trailing arms (sods law I've already ordered a complete bolt/bushing kit for the 90 as part of the re-chassis).

Whilst you may be able to use the callipers from your existing axle, use the bolts from the axle/swivel housing you are going to use. I had an issue when I did my axle as one calliper was stuck and very old, the other relatively new as it had obviously been replaced in the past. The calliper that was older (and in desperate need of replacement) had the bolts rounded off. It took some effort to remove that calliper, including cutting the calliper in half to access the rear of the bolt plus drilling, heat, plusgas and bolt extractors - however I eventually got that off and realised the bolts were a course thread, so I had to go and get a set of these.

However, the other side had been replaced and the person that did it had used fine threaded (later style) bolts. I presumed the bolts would be the same each side and so fitted course thread bolts. The original calipers had obviously been fitted with course bolts, but the replacements had used fine thread - this ended up with me fitting course thread into them but the previous use of fine thread had obviously taken its toll and when it came to torque them up. The bolts would not register any torque due to the damage and I ended up having to use helicoils to repair the damage.

Brake caliper stripped thread - OK to helicoil?

In the course of refurbing my swivels and hubs, I have stripped a thread when refitting the brake caliper. It seems odd that this one has stripped as it was the other side that needed action to get the bolts out - typical! BTW I was using a torque wrench when putting the bolts in. So, can I fit...

www.landyzone.co.uk

MrF · Jun 10, 2023

Yes, I'll use the fastener that matches its pitch with the mating part thread. I didn't remember if in this case it screwed into the caliper, or if it screwed into the hub casting & both front axles haven't been broken down yet to refresh my memory but thanks for the warning.
This weekends task is to move everything to the washing space of the yard so I can steam clean it all off properly & further disassembly. Provided the forklift is in a good mood

jockstrapjungle · Jun 23, 2023

MrF said:
Looking for some input on something I'm trying to do.
Backstory, I have a 90 that I've owned for 20 years that I'm finally rebuilding with a new chassis that I'm waiting for shipping notification hopefully today and because I have to replace brake lines/steering box etc while I'm doing this, I'm doing a lhd + 200tdi swap as its a approved engine type for this year here, and my 19j is done, 150k miles + a turbo runaway at 130k.

I've sourced that mythical creature, a reasonably priced extremely rotten discovery1 and its given up its components for this project, but when it comes to the front axle I have a issue in that I want to stay on the 90 rear axle with drums because a disc braked rear axle is too new for this vehicle (1990) and it might get checked on inspection. There's nothing wrong with my original 90 front axle apart from the challice balls aren't perfect and it has rhd hub castings.

So I could swap to the discovery front axle, and I read about the location arms being wider and I still have them from the donor disco. But it has the RR/Discovery dual circuit front calipers. Again because of eagle eyed inspectors I cant just run two brake hoses and a tee piece or loop the two ports because it'll be obvious I swapped in a disco front axle to someone who knows their stuff and I'm trying to be discreet.

soccer random
So what are my options?
1) can I rebuild the 90 axle with just the lhd modified casting from the disco axle? Im thinking this is a no because the 90 axle is the older ralco top bush pivot setup and the discovery will be dual taper bearing pivots, but someone probably has experience having tried the same.

2) can I rebuild this discovery1 axle with the brakes from my 90 and keep the year correct unvented solid front discs setup. They've been good enough for 20 years, so not sure I need the improved power of vented brakes.

3) if 1 and 2 are not recommended, can I pick up a pair of defender front calipers from a early vented disc model & just bolt these on (and try to blag them as factory substitute parts). What about piston diameter and master cylinder bore sizes when remembering I have to keep the drum rear end?

So any experienced based answers to the above? I'm not scared of the work, but I want to keep it at the parts swapping level rather than fabrication.

I believe a 200 tdi. I switched to vented front brakes because I got them for a good price. When I finally got it off, I saw that the bolts had a coarse thread, so I had to go get a set of these.

MrF · Jun 23, 2023

Last update, its all sorted. Both axles had solid front discs in the end so it was just a caliper swap & retained the fasteners that matched the swivel housing casting thread.
Fettling the rest of it now while I wait for the chassis supplier to get their act together still.

90/ discovery front axle swapping

MrF

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Dr Strangeglove

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Anaconda

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MrF

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Dr Strangeglove

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Brake caliper stripped thread - OK to helicoil?

MrF

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jockstrapjungle

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MrF

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