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V8 Autobox conversion


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Having spent a year finishing my "it'll be done in a month" V8 conversion I'm not happy with the LT85 box. Bag of hammers sums it up.

So while I'm at it might as well go auto?

I've searched (honest) and done the google 'lr4x4' bit but I'm struggling.

I've read somewhere that a Range Rover autobox is the same length as an LT85 with long bellhousing? So it's just a case of robbing a Range Rover for donor parts then it's all just nuts 'n bolts (+tea, cigs, etc.)?

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Guest noggy

yeah, just get a RRC with a drowned v8 or something, swap the parts over.

i believe the 3 speed auto box was a better box than the 4 speed.

but i stand to be corrected!

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Your going to need the box(with torque converter/flexplate),mounts(RRC),g/box crossmember,RRC front prop,box wiring loom and gear selector.......and that should be it. Only thing that will obviously need fabriacating will be the transmission tunnel and a bit of modification of the gearbox crossmember

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Hattymender,

I have just done this exact same job.

Yes the LT85 (I believe only 1 size of bell housing exists) is exactly the same length as the 4sp auto from a RRC, or Disco 1.

If you stick with your LT230 transfer box you won't even need to change the prop shafts. The Borg Warner transfer however will need a shorter front prop.

Depending on what engine you started with before your V8 conversion you'll need to resculpt or change the tunnel. The LT85 hi-lo stick is much further forward than all the 4 cyl variants so the tunnel opening will be in the wrong place. I shall be using a R380 tunnel as used on 300Tdi and Td5. 200Tdi tunnel is much smaller.

As LittleBlue88 has said all the parts you need can be found on a RRC. I will add the transmission oil cooler to the list, forget that and you'll most likely cook the box. All that's needed loom-wise for the box is the 4 wires, 2 for reverse lights and 2 for start inhibit.

As Bishbosh has advised, it's much easier to have a whole car to rob for bits as you think of them.

3 spd auto is stronger than a 4 speeder but will rob you of more power, is not so readily available these days either. Stick with the 4 spd, absolutely nothing wrong with it.

If you have any other questions feel free to ask while it's fresh in my mind.

Cheers,

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Hattymender,

I have just done this exact same job.

Yes the LT85 (I believe only 1 size of bell housing exists) is exactly the same length as the 4sp auto from a RRC, or Disco 1.

If you stick with your LT230 transfer box you won't even need to change the prop shafts. The Borg Warner transfer however will need a shorter front prop.

Depending on what engine you started with before your V8 conversion you'll need to resculpt or change the tunnel. The LT85 hi-lo stick is much further forward than all the 4 cyl variants so the tunnel opening will be in the wrong place. I shall be using a R380 tunnel as used on 300Tdi and Td5. 200Tdi tunnel is much smaller.

As LittleBlue88 has said all the parts you need can be found on a RRC. I will add the transmission oil cooler to the list, forget that and you'll most likely cook the box. All that's needed loom-wise for the box is the 4 wires, 2 for reverse lights and 2 for start inhibit.

As Bishbosh has advised, it's much easier to have a whole car to rob for bits as you think of them.

3 spd auto is stronger than a 4 speeder but will rob you of more power, is not so readily available these days either. Stick with the 4 spd, absolutely nothing wrong with it.

If you have any other questions feel free to ask while it's fresh in my mind.

Cheers,

Thanks for the offer, at this stage I don't know what I don't know but I do know I can't live with that box for much longer but I've pushed my luck with the wife's patience and my massive underestimating of how long jobs take. I was hoping to avoid moving engine, exhausts etc as costs and agro seem to go up massively when these 'incidentals' are factored in.

I bought the V8 as a job lot; engine, gearbox, transfer box, props, etc. so I've got both LT85 and LT77 tunnels, props etc. Plus in spares bin a LT77 & transfer box (& 2.5 petrol engine) and a very chopped about and patched seat box.

Given the level of agro involved in converting from 4 pot to V8 I was hoping to keep it down to a nuts 'n bolts job except for a bit of 'creative fabrication' to accept the selector. While I was at it with the V8 I swapped the seats for Citroen AX jobs, binned the center seat and put in a Range Rover hand brake lever so I'm part way there on making space.

My shopping list was; Auto box, selector, kickdown cable & brackets, auto flywheel & torque converter, oil cooler + wiring.

Then just bolt it all up? Easy?

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Rich

Regarding your comment about the LT85 sounding like a bag of hammers, these boxes are renowned for the bearings becoming a little noisy after a time. Even when healthy they are agricultural when compared with an R380. However the LT85 is a good strong box, ideally suited for the rigors of life behind a V8.

I rebuilt my LT85 with new bearings and it quietened it down a fair bit but the noise returned after a few years. The main and layshaft bearings are huge, and despite getting a bit rumbly I can't see them falling apart. I remember seeing inside an LT77 once and couldn't believe how small everything was.

Obviously yours must be pretty noisy if you can't live with it. Have you thought about rebuilding the box? Not that expensive a job, but does require a few specialist tools such as a good bearing puller. At the time I had no puller but made up tools for doing specific operations as per the green bible.

If you're not up for a DIY rebuild, Ashcrofts charge £550 (plus VAT?) for an exchange box. Expensive as that may sound it could work out less time and hassle than an auto conversion.

Good luck which ever route do decide upon.

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i'd also consider looking at the R380 route tbh

You'd probably need a disco V8 box fitted with the tail housing from a defender R380, so a bit of messing around, however its messing around that can be done with the vehicle still in one piece, and should result in a bolt in conversion using defender R380 crossmember and your existing V8 mounts.

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