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Hi all,

I am currently planning on doing a 6X6 conversion on a defender 90 but i can't find anything for the drivetrain

please help

Thank you

Edited by western
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  • western changed the title to 6x6 conversion

I believe there are several ways of modding the driveline. Depends if you want the full 6wd or just a 6x4. For road use, such as a transporter the latter would be fine. But if you plan to go off road you'll likely want the fully 6x6 experience.

Certainly worth spending some time searching the forum and Google for what has been done prior. I believe someone has even used electric drive for one of the axles.

Do you have a particular intended use for the vehicle?

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29 minutes ago, FridgeFreezer said:

@Chicken Drumstick that's a 6x6 Volvo C303 with a 110 on top, so yeah all sorts of better - ground clearance, gearing, lockers, diffs not made of cheese...

Thanks. I came across it ages back, but wasn't sure if it was a Land rover running portals or a lot more modified. Is it also using the C303 chassis/engine?

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27 minutes ago, Chicken Drumstick said:

Thanks. I came across it ages back, but wasn't sure if it was a Land rover running portals or a lot more modified. Is it also using the C303 chassis/engine?

Rear axle mounting pivot is very C303 and the way the chassis pokes out the back / front steering arrangement suggests it's more C303 than LR - the Finns did have a shortened 6x6 C303 that was not much longer than a stock 110 so I'd wonder if this is along similar lines.

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Right since I was called out I'll try and provide some first-hand experience (I've got a couple of 4x4s, a 6x6 and an 8x8).

You say off-road and towing but what kind of off-road and what kind of towing? If it's relatively flat stuff then that simplifies matters a huge amount, if it's a camper trailer than that's one thing if it's 3.5t then that's a different ball-game. Is the towing happening off-road? What are your requirements on actual finished length? In general I'd wholeheartedly agree with @FridgeFreezer that most 6x6s are for extra payload or posing.

3 hours ago, bradley said:

I will usually use it to tow things and a 6x6 is better in slippery conditions as it has more traction

It depends completely on the surface - if a 6x6 is an equivalent weight to a 4x4 then you've got less ground pressure so on some surfaces that might help because you don't break through the surface but on others you don't have as much traction because of the lower ground pressure.

I can go into far more details if you want but if you want two closely coupled rear axles like you have drawn then either a bogey setup or what has been done on my Sandringham 6x6 is the best solution for the drivetrain. The "drop-boxes" that bolt onto the front of the middle diff mean that you get into a world of pain with propshaft angles and the like. If you put two propshafts from the rear of the transfer box you get into problems with clearance and prop angles again. There have been through-drive diffs done by having a sceond pinion on the rear of the crown wheel but I've not heard anyone who's been complementary of that design.

I've given 6x6 and 8x8 drivetrains quite a lot of thought over the last few years as I've been asked to potentially build up a couple and also have some friends who've built them in the past (one did the Defenders in the Expendables film and another has done a number for clients and his forestry business). I can provide a lot more details on upsides and downsides of different drivetrains but you'll need to have a long hard think about what you actually want to achieve with it.

For a basis my Sandringham 6x6 came out of a requirement by Land Rover to produce something that had greater payload and lower ground pressure but still capable off-road. They reached out to Hotspur and told them to design something but keep as many components as off-the-shelf as possible. So apart from most of them being reasonably rare there are only a handful of "custom" parts that aren't standard Land Rover ones. It started life as a Stage 1 V8 before having the chassis plated, strengthened and lengthened. Springs, brakes, wheels etc., are simply the biggest heaviest duty ones available from LR at the time. The only bespoke bit of engineering other than the chassis was the middle diff which was a modified Rover casing with a custom drop-box bolted to the front.

It's plated for a 2 tonne payload on the back and 4 tonne towing capacity (no mention of coupled brakes but this was before they were really a thing) so gross train weight of 5kg under 8 tonnes. Despite being a 6x6 Land Rover it's only a foot longer than a 110 and doesn't turn anyworse than one although you do scrub some wheels because the two rear axles are permanently connected.

Answer some questions and I can offer more help but this post is long enough as it is :hysterical:

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Bradley - what sort of off-roading / events are you looking at? Without knowing your level of experience etc. it's very hard to know what your definition of "mudding & wading" is.

And a stock 90 will tow a "massive trailer" quite happily, so again you probably need to give some example or we're just kinda guessing.

You're proposing a very drastic and potentially expensive build with a lot of drawbacks and there's numerous other ways to improve off-road ability, towing/recovery/load carrying that are far more common and easier done.

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12 minutes ago, FridgeFreezer said:

You're proposing a very drastic and potentially expensive build with a lot of drawbacks and there's numerous other ways to improve off-road ability, towing/recovery/load carrying that are far more common and easier done.

Yes undoubtedly, but it is kind of fascinating......

Foers used to offer 6x6 - not sure what they used for the driveline. I do know without a third diff between the axles there will inevitably be windup, hence Ed's Sandringham using freewheel hubs. All full size trucks have 3rd diffs. Off road  or lightly loaded it may not matter, though
 

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Note the freewheeling hubs were fitted by the previous owner not from factory. I've almost never run them unlocked as stuff around here is too hilly so I struggle at junctions etc (although I do need to rebuild the leaves).

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In Australia we have plenty of 6x6s sold off from the Army a while back - as mentioned good for carrying load and good for traction in open country but they are no good in tight offroading scenarios.

 

 

 

 

perentie.jpg

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4 hours ago, cackshifter said:

Yes undoubtedly, but it is kind of fascinating......

Foers used to offer 6x6 - not sure what they used for the driveline. I do know without a third diff between the axles there will inevitably be windup, hence Ed's Sandringham using freewheel hubs. All full size trucks have 3rd diffs. Off road  or lightly loaded it may not matter, though
 

Foers still do a 6x6 version of the F8 ibex and it's very cool. 

https://www.ibexvehicles.com/

Mike

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Here's the Finns shortened & bobtailed 6x6, it works very well but it's got a lot more going for it than just an extra axle.

Parked alongside a Camel 110 behind it and almost exactly the same length. Tyres are 40's I think.

C303_6c6_Bobbed.thumb.jpg.4df14f19e4bb8cca2b656856485d7a3d.jpg

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