Building the gearbox of my dreams

I got a bonus at work at the end of November, so what better way to mark the occasion than to waste it on Land Rover accessories?
I've been bending the plastic over the past few days. An overdrive unit arrived:

it even has a cute little finned sump for the transfer box to help keep it cool:

There was also a package from Mr Ashcroft. Here's a limited slip centre diff waiting to be fitted:
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So today being the first opportunity to get some Land Rover maintenance done, I started work. It was going to be a lot easier if I got the seats and matting out of the way, as well as the transmission tunnel. This was no mean feat as every screw was rusted solid. The transmission tunnel itself is made of plastic so you can't be too vigorous with it. Having blunted a lot of drills on the heads of the screws, I finally got it away. The spongy rubbery matting is pretty tough too, and it's all been fastened on behind the fusebox and air conditioning unit so there was quite a bit of minor dismantling to do. At last I had some room to work:


The way this works is that you take the back off the transfer case and bolt the overdrive unit on. Here's the old bit extracted:

That tapered roller bearing on the end needs replacing. Here's a new bearing being tapped onto the input shaft of the overdrive unit:

Getting the outer shell of the old bearing out of the transfer case was a bit more interesting. Fortunately I could just reach it with a hook on the slide hammer, and it came out quite readily.

New one tapped in and we were ready to offer up the new unit and see if it fitted. Here's the new input shaft with its new bearing:


Yes!! It fits. A drop of gasket sealant and I tightened it fully home. The light was going at this point so the picture's a bit dim:

Time to come in for a cup of coffee.

Looks interesting! I'm guessing what you'll end up with is a 4-speed transfer box and no separate difflock? If that's the case, it would be quite neat if the original transfer lever left/right motion (old difflock control) could be tied into the overdrive unit gearshift- so push left to engage overdrive.

I'm also changing some bits on the handbrake while I've got everything apart. No pictures of this, but I've changed the adjuster and the cable. It's very sharp now - never mind three clicks, it's more like one and a half. However the end of the cable sheath won't go in the hole in the backplate properly. I had thought that heaving on the handbrake lever would pop it in, but it doesn't seem to want to go. I might have to take it apart again and file the hole out a little. But a new cable really makes a difference. if it wasn't for the permanent four wheel drive I'd be able to join the young kids drifting in the supermarket car park.

Getting the sump off the transfer box was a bit of a struggle too. Most of the bolts were seized and they're the sort with little teeny heads and built in flanges. So that took a while. Even so, everybody's out now and no one's snapped, so no drilling needed. Something happens to Land Rover's plated steel bolts when they're in prolonged contact with alloy castings, and they don't want to shift.

Being a TD5, mine has monster wiring looms which of course are in the way of the overdrive shift mechanism. I shall see if I can do a bit of cable re routing so nothing's fouling. Maybe I'll put the overdrive control rod in a tube of its own, so it just rubs the inside of the tube and not the wiring looms. There isn't very much room on the nearside of the gearbox where it passes through the seatbox. It's got to accommodate two big fat wiring looms and an overdrive shift mechanism.

Work permitting, I will have a go at the centre diff housing tomorrow and see if that'll come off.

FlyingPete said:

Looks interesting! I'm guessing what you'll end up with is a 4-speed transfer box and no separate difflock? If that's the case, it would be quite neat if the original transfer lever left/right motion (old difflock control) could be tied into the overdrive unit gearshift- so push left to engage overdrive.

Click to expand...

Yup, it effectively gives you two more speeds, so you've got the five speeds in the main box, two in the transfer box and another two via the overdrive. So that's twenty gears altogether if you were to use all of them. But mainly I'll be using it to make things a bit more relaxed and economical on motorway trips.

With the limited slip unit in the centre diff housing, it's still lockable in the normal way if you want to. So all the functions of the existing gear levers are needed! I go to Wales a lot, so I find myself on a lot of slippery surfaces, and it's just nice to be able to get a little bit further before needing to lock up.

does diff come with any shims or do you order the seperately

jamesmartin said:

does diff come with any shims or do you order the seperately

Click to expand...

None in the Ashcroft's box, but I've stocked up on various diff housing bits elsewhere, because I'll be changing the bearing and seal too. I've also freed up the mechanism for the transfer box and centre diff. The bit in the housing at the top was choked with rust. It's a lot sweeter now.

I've been thinking of getting one of the Roamerdrives on my 110 as I plan on keeping it a while and we generally do a 4000 mile round trip on the motorways across Europe to visit the other half's family every summer. It would be nice to cut the revs down a bit. Hurry up and get it done as I'm keen to read your opinions on the difference they make

jonny2tanx said:

I've been thinking of getting one of the Roamerdrives on my 110 as I plan on keeping it a while and we generally do a 4000 mile round trip on the motorways across Europe to visit the other half's family every summer. It would be nice to cut the revs down a bit. Hurry up and get it done as I'm keen to read your opinions on the difference they make

Click to expand...

I do quite a lot of long trips too. I was wondering about the 1.22 discovery ratio, but I quite like the gears where they are for everyday use around town. So with my recent bonus the Roamerdrive was just too tempting. After all, whilst it's quite dear, it's no more than a lot of people on here spend on a galvanised chassis or a winch. I'm looking forward to getting out on the open road once it's all finished, because by the time I get up to about 60 or so I'm feeling around for a higher gear and of course under normal circumstances there isn't one.

Brown said:

Yup, it effectively gives you two more speeds, so you've got the five speeds in the main box, two in the transfer box and another two via the overdrive. So that's twenty gears altogether if you were to use all of them. But mainly I'll be using it to make things a bit more relaxed and economical on motorway trips.

With the limited slip unit in the centre diff housing, it's still lockable in the normal way if you want to. So all the functions of the existing gear levers are needed! I go to Wales a lot, so I find myself on a lot of slippery surfaces, and it's just nice to be able to get a little bit further before needing to lock up.

Click to expand...

Yeah I guess it would still be useful to manually lock up the diff for no slip. If it was me, I'd like to have the overdrive electrically operated, so you could have a switch for it in the main gear lever. Most useful as a sixth gear for more relaxed cruising I guess

Brown said:

I do quite a lot of long trips too. I was wondering about the 1.22 discovery ratio, but I quite like the gears where they are for everyday use around town. So with my recent bonus the Roamerdrive was just too tempting. After all, whilst it's quite dear, it's no more than a lot of people on here spend on a galvanised chassis or a winch. I'm looking forward to getting out on the open road once it's all finished, because by the time I get up to about 60 or so I'm feeling around for a higher gear and of course under normal circumstances there isn't one.

Click to expand...

I've followed a few of your trips on here, and I know the feeling about going for another gear . I've been considering a few things: a Disco transfer box but feel this would need a remap (which is on the cards anyway, just don't tell the other half) to keep the 'performance', the Ashcroft fifth gear mod and the Roamerdrive, and am favouring the dearest - the Roamerdrive, mainly because it would probably be the easiest to take off when I eventually do sell the car and either fit it to a newer 110 or sell on.

jonny2tanx said:

I've followed a few of your trips on here, and I know the feeling about going for another gear . I've been considering a few things: a Disco transfer box but feel this would need a remap (which is on the cards anyway, just don't tell the other half) to keep the 'performance', the Ashcroft fifth gear mod and the Roamerdrive, and am favouring the dearest - the Roamerdrive, mainly because it would probably be the easiest to take off when I eventually do sell the car and either fit it to a newer 110 or sell on.

Click to expand...

Yes, I'd probably need a remap to get the very best out of the overdrive too, so as to be able to use a higher gear at lower revs. But that's not on the cards for another year or two.

Yes, an electrically operated overdrive might be nice. However, the lever operation is nice and simple and, because you've got to use the clutch, having something like a gearchange with a lever will remind me to do so. A button would be too tempting just to press, and I might damage something.

I'm hopeful that the Romerdrive/Roverdrive will give me lots of trouble free motoring. I can't see anyone on the internet who claims to have broken one.

Once it gets light I'll go out and do a couple of small things before I have to go into work at 10.

Here's a brief report on today's activities. It doesn't look like much but there was a lot of time spent freeing off bolts that didn't want to come undone without snapping them or rounding the heads off. First I filed out the hole in the handbrake backplate to fit the new cable outer. Forgot to take any pictures of that. Then I ground off the screws securing the driver's side floor panel to give me a bit more room. On reassembly I'll put 6mm stainless nuts and bolts in wherever I can, instead of the clip on captive nuts and the square plastic captive nuts that have given me so much trouble this time around. It will be inconvenient needing a spanner top and bottom if I ever need them undone again, but it'll be a lot easier than what I've had over the last two days.

Here's the overdrive in daylight:

Now it's time to undo those little twiddly levers that link the transfer box lever to the bits that do business:

Seems a bit remiss of Land Rover to rely so heavily on spring clips in such an inaccessible area, but there you go.
Getting the front nose cone off the final drive necessitated a bottle jack under the transfer case because one of the gearbox chassis mounts is bolted to it. I wedged the gearbox aloft with some blocks of wood in the cross member:


That gave me enough room to work. The bolts, needless to say, did not want to let go. I think it's something to do with the first six years of the Land Rover's life at Swansea power station. A maritime climate and a covering of a hard grey cementitious material, probably power station ash that's gone hard with salty water. Plus I missed one of the bolts, so spent ages tapping and rattling the thing before finding the head of the last one under the grey cement. Off. finally:

Now let's get the nut undone - wheee:

after another epic with the seal and circlip, I pulled the bearing off the output shaft, ready for the new one. I'm glad the puller is a 10 ton one otherwise I'd have been a bit stuck. It might have been glued on with Loc-Tite Quick Metal or similar. I hope that doesn't mean it's undersized and the new bearing will be loose.


In other news, the centre diff itself does not merely slide out on its splines in a civilized fashion, but as I'm sure James and Aaron could have told me, it is integral to the transfer case mechanism, so more dismantling is needed. I started taking some more bits off, but ran out of light. So my handbrake had to come off again for the third time in two days. Rather than trying to dismantle and reassemble the transfer case whilst lying on my back and working overhead, maybe I should take the transfer case off completely and work with me the right way up and the transfer case upside down.

there is a 6mm allen key size grub screw on side of box top rear that needs removing and youll need interrmediate gear out to remove diff plus set up diff shimming

Ah, James, it didn't take you long. That's useful. At least I know what to look for under the cement. It's rough stuff, like Tyrolean rendering that takes the skin off your hands and shreds rubber gloves. If it's an intermediate shaft out job I think I might take the transfer case off completely. I did this lying on my back with the old Series 30 odd years ago, with me holding the gears up and my brother trying to get the shaft in, but I'm single handed now and 50 something rather than 20 something.

it wont come out unless box is off unfortunately,an engine crane makes life easier

In which case I might start taking it off tomorrow if I get a moment. I haven't got an engine crane but at least with the fancy new sump it'll have a horizontal flat bottom so I can build myself a little plinth to rest it on to aid reassembly.

Had a couple of hours on it this morning. Right, let's see if we can drop that transfer box:

As usual, the bolts were tight and seized beyond the leverage I could apply manually lying on my back. Fortunately they yielded to the mighty Milwaukee without snapping or rounding off. The more you take apart, the more you realise needs doing. One of the gearbox mounts is separating. This one's bolted to the gearbox so you don't strictly need to take it off to get the transfer box out, but I saw that crack and thought I'd better do something about it:

I undid the transfer case and tapped it loose. Some of the fastenings are studs rather than bolts so, I worked it off the studs and let it drop. Aaagghhh! There are still some wires attached:

Fortunately they're only earths, but momentarily they took the entire weight of the box. I hope I haven't yanked them out of something sensitive at the other end. Fortunately the transfer case, whilst heavy, is just about liftable by one person so I should be able to get it back on.
Yes, it's much easier on the bench. Intermediate shaft out, final drive shaft out:

That's about as far as I've got today, as I need to go out now. I'd better fit new bearings as well. Those ones are a bit scored and pitted, though it doesn't show up on the photograph. Even the intermediate shaft has tapered rollers too. My goodness me how times have changed from the old Series days. The intermediate shaft rollers are lovely and shiny so I think I can reuse them.

Looks like I'll be filling an electronic basket at LR Direct. I want some bearings, and a gearbox mounting rubber, and it's good practice to replace those nuts of the kind that you lock by bashing a bit down into a groove on the shaft. With new bearings and a new diff centre I might invest in a handful of spacers - I see the parts catalogue lists them in 0.05mm increments - to get the bearings running as best I can. Plus my speedo sender unit seems to be disintegrating and it is full of a mixture of road dirt and rust. It's amazing I was getting a speedo reading at all. My bits probably won't come 'til after Christmas now so it'll be a while 'til I'm back on the road. So much for a quick job.

On the plus side, the box isn't full of ground up metal. The only crap I found was a tiny flake of bronze in the front nose cone I took off yesterday. Bit of a burr off one of the sliders, I think.

Very interesting, thanks for writing about it ..

While the transfer if off and you have 'nothing to do over xmas' is it worth pulling the main box off and changing clutch etc if it is high mileage as you are 75% of the way there already?

diff bearings are 606474g and frc7871g, g as you want timken,wires are earths for the electronics it wont run without them,early lt230s did use roller bearings like the series and you still see a few around,later are lt230t t for taper bearing, you need a new collapsible spacer to go between intermediate bearings frc7437