Building the gearbox of my dreams

I can't show you pictures from today because Photobucket seems to be down. I'll edit them in when it's back online. I took a long trip (well, 120 miles) to Wales as I'm making some new garage doors at my mid Wales friend's house. I loaded up the roofrack with wood and filled the rear compartment with tools of every shape, colour and creed known to humanity, plus hinges and bolts and set off. Photobucket's available again so here's a picture:

Heading westwards into a headwind with a roofrack on took the edge off the performance a little. The transfer case oil temperature crept up on the fast bits of road, which was from the M69 junction at Leicester all the way to Shrewsbury. I was really cooking on the last bit of dual carriageway between Telford and Shrewsbury. I read that the flashpoint of GL4 EP90 is about 190 C so I'm not in any danger of setting the gearbox on fire just yet, But it was certainly warm. On the road from Shrewsbury to Newtown it cooled down. I assume it's still running in, so will let it settle over the next couple of thousand miles and then change the oil again. Here's me on the map:


Once in Newtown I was confronted with another problem. My friend couldn't get his R380 gearbox into gear. 'It's broken' he lamented 'I'm broke, I can't afford a new gearbox, they're hundreds of pounds'. I got in and tried for myself. There was no resistance (other than the return spring) on the clutch pedal so I surmised it was more a clutch problem than a gearbox problem.
The cap of the fluid reservoir wouldn’t come off. Eventually I turned it with some oil filter pliers I bought myself for Christmas. There was fluid in there but it was dark brown. I used the pressure bleeder for my brakes to pressurise the system and lo and behold it would change gear. So it must be a hydraulic problem. I bled it, and bled it some more, but it still wouldn’t work unless it was under pressure. Eventually I managed to blow some air out and it is now much better. I can change gear from stationary and on the move. I’ve only been along the lane by his house in it, but it seems OK. The fluid was the filthiest dirtiest stuff I have ever seen in a hydraulic system. There’s been no maintenance done on that car despite its main dealer service history. Anyway, I hope it's just the fluid degrading and that it's not dissolved its seals. Then I ripped the side off the shed where we're going to fit garage doors, and then it was time for tea.

Just a small update. While servicing the car today I changed the oil in the transfer box and changed the seal and flange at the front propshaft side, because I have a tiny oil leak there. There was a little bit of metal dust on the magnet in the drain plug, but probably not enough to worry about. The oil was quite dark too, so I'm glad I changed it. The tendency to heat up is diminishing as time goes by. I make trips from Leicester to Nottingham quite regularly and look at where the temperature gauge is at various points in the journey, and it's a little less every time.

Brown said:

Just a small update. While servicing the car today I changed the oil in the transfer box and changed the seal and flange at the front propshaft side, because I have a tiny oil leak there. There was a little bit of metal dust on the magnet in the drain plug, but probably not enough to worry about. The oil was quite dark too, so I'm glad I changed it. The tendency to heat up is diminishing as time goes by. I make trips from Leicester to Nottingham quite regularly and look at where the temperature gauge is at various points in the journey, and it's a little less every time.

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I've been meaning to ask how the Roamerdrive is going. I'm slowly getting through to the other half that we really need one, but it's tough going. She likes to leave cars standard and if something goes wrong with a car she always blames anything that I have just done to it for it, even if it's not related to what's gone wrong. You wouldn't think it was my Defender the way she carries on. Last weekend we did a motorway trip and I was taking every opportunity to point out that the engine revs at 70 would be what we are currently doing at 50mph if we had the overdrive unit so the engine would be under less strain and it'd be quieter for our 1600 mile each way summer trip to Belarus. How are you finding the fuel consumption? Is there any significant difference? They also talk of gear whine when the unit is first fitted until it beds in (10,000 miles or so). Have you experienced any particular extra noise?

The most noise I had turned out to be the gear knob having loosened and was rattling. Maybe the transmission sounds slightly different now but if I didn't know there was an overdrive fitted I wouldn't be able to tell, I don't think. There was a peculiar noise when I went to Wales about five weeks ago which I couldn't place, but that turned out to be the wind whistling in the roof rack. I suspect the fuel consumption might be a little better. I got a trip to Cambridge and back plus a trip to Nottingham and back for £42 a couple of weeks ago, which seemed like good value, and considerably cheaper than the train fares would have been. But there are often other factors at play, such as having loads of wood on the roof rack, strong headwinds, and how much stuff I have in the car that probably make a difference too, so it's hard to be precise.

It wouldn't take long to put things back to standard if you wanted to. Just take the overdrive off and put the original backplate and input gear back in the transfer case and away you go.

The ability to put it back to standard quite easily is the attraction of the Roamerdrive. I'll keep plugging away at her (or more than likely do what I did with my last Defender and had a remap, decat and centre box removal whilst she was away and didn't tell her. The first time she drove it when she came back she phoned me and said ;there's a whistling noise, like a turbo'. I replied 'that'll be the turbo working then, better than not hearing it which will mean it's buggered'. She never did know the truth, but she might notice an extra lever )

Good stuff brown, this may be on the cards for me in the future once I find out how mine behaves after the rebuild. Would you say this is more worthwhile than a discovery box with its longer gear ratio?
Jonny - just crack on mate, haven't you heard the saying 'it's easier to get forgiveness than permission'? I feel for you, I've been there myself with a whinging cow who complains about every penny and every minute but seriously, what's she gonna do about it? Same as the rest of them - NOTHING! That's what.

Personally, I prefer it. As said earlier, I quite like the gear ratios where they are for trundling round town, with traffic lights, 30 and 40 mph limits and suchlike - they seem to work quite well.So it's nice having an extra gear to shift into when you're up to about 60 or so. Having said that, it's a lot more expensive than a secondhand Discovery box. But then it's comparable to what would spend on a new chassis or a Warn winch or one of those similar big ticket Land Rover Items. I like going on long trips and setting off at 5 or 6 a.m. so as to get a couple of hours driving in before the roads get seriously busy. In which case it's good for me going to Wales or Scotland (though I haven't taken it to Scotland yet). I can't see anywhere on the internet where people claim to have broken one, so they are probably fairly reliable. So it seemed like a good use of my bonus last autumn.

Finally, after three months I have some of the transmission noise people say is associated with these things. It sometimes makes a noise at speeds below 50 mph. Maybe it makes a noise at speeds higher than this too, but it's either so high pitched I can't hear it or is drowned out by the other Land Rover noise. But there's an intermittent noise at about 20-40 mph that seems to have a frequency of about the speed the transfer box is spinning at. Not overwhelming, just letting me know it's there.

Another update for the summer of 2016. I was still getting some high temperatures, especially with long motorway trips. It's not the load or the power that heats it up, it's the speed. So I've added an oil cooler. Poor quality pictures taken with a mobile phone, but you can get the idea.



Plus, as it's not going to go round merely by convection, there's a pump:



This is triggered by a temperature sender I've tapped into the transfer box sump. This keeps temperatures down to around 100 C which is where I want them to be. There's a slight vulnerability in having the additional components underneath, but they're tucked up well above the chassis rails and I spend a lot more time on motorways than I do rock crawling.

That's altogether a cracking upgrade. So you think the extra heat is from increased friction from going faster? Do you have any idea what temperature it was getting up to before you put the cooler in?

Al2O3 said:

That's altogether a cracking upgrade. So you think the extra heat is from increased friction from going faster? Do you have any idea what temperature it was getting up to before you put the cooler in?

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I'm just looking at the little temperature gauge from Roamerdrive, so I don't suppose it is wholly accurate, but if I sat on the motorway for a while and kept up with the white van men, I could get the needle up against the stop at the end! Now it is much better. If you drive everywhere at about 50 or 60 you'd probably not overcook it at all, even without a cooler. I think it is not so much friction (after all, there are a lot of ball and roller bearings in there) but the heating effect when a fluid is mashed around at high speed. Rather like those new powerful blenders that make soup by using this heating effect https://www.youtube.com/user/FroothieTV . It's even possible to detect it in waves on the beach http://onlinelibrary.wiley.com/doi/10.1002/2014GL061398/abstract - these folks call it 'viscous dissipation'.

Interesting idea regarding the oil cooler, any chance you could snap a few more photos including where the outlet and inlet are on the case - presumably somewhere on the finned sump?

I noticed that my entire transfer tunnel seemed to be a lot warmer this year on my drive to/from France, my guess is that it's down to the slight difference in diff ratios between front and rear (3.75 rear, 3.8 front) since fitting the locker and that this in turns means the centre diff is working a little harder.

Anyhow I'd be interested in doing something similar. Ta.

Bennehboy said:

Interesting idea regarding the oil cooler, any chance you could snap a few more photos including where the outlet and inlet are on the case - presumably somewhere on the finned sump?

I noticed that my entire transfer tunnel seemed to be a lot warmer this year on my drive to/from France, my guess is that it's down to the slight difference in diff ratios between front and rear (3.75 rear, 3.8 front) since fitting the locker and that this in turns means the centre diff is working a little harder.

Anyhow I'd be interested in doing something similar. Ta.

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I didn't take any pictures of modifying the sump, but I'm sure you'd be able to work it out given all the other mechanical feats that you do. The high capacity finned sump has flat areas front and back so I installed -8 JIC tank connectors in a kind of cross flow pattern (cut the holes with one of those stepped sheet metal drills), hose connectors and appropriately sized hose. I've piped it so the pump is pushing the oil through the cooler matrix, so it doesn't have to suck too far, as it's the sort with a gear mechanism. I got a 22mm Intermotor temp sender and tapped a 22mm threaded hole into the sump for it. You can get them in various specs to switch on and off at the temperatures you want - I think mine's a 68-82. I've run a switched live from the ignition switch that goes to the temp sender, then a wire going into the battery box which triggers a relay that powers the pump.

Anyway, that should give you some idea. Now I have been on a few long trips and I know it's working reliably I might sort out a somewhat neater pipe routing! You've got a Discovery as I recall so no doubt you'd want to position things differently.

How's the rebuilt TD5 engine going? Behaving itself?

Engine is doing great since the rebuild, it's had 20K on the clock since. I'm still chasing a small injector idle imbalance that I managed to introduce recently after refreshing the fuel pump, filter block, injector seals following a pump failure - really frustrating. I've redone the seals and washers 4 times now with not much change. There must be air getting in somewhere but it doesn't affect performance at all, just a slightly annoying idle :/

About three years ago I was getting some very large cylinder balance values and occasional 'high speed crank error' codes which I eventually cured by fitting a new crank position sensor. Prior to that I thought crank position sensors were an all-or-nothing affair - they either worked or they didn't. But clearly there can be shades in between, especially when they're budget Britpart items.

Brown said:

About three years ago I was getting some very large cylinder balance values and occasional 'high speed crank error' codes which I eventually cured by fitting a new crank position sensor. Prior to that I thought crank position sensors were an all-or-nothing affair - they either worked or they didn't. But clearly there can be shades in between, especially when they're budget Britpart items.

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I renewed the shielded cabling to mine which made no difference - I suppose it could be the sensor but the problem only started after doing the fuel system changes.

I might see if I can borrow a sensor from a friend to test it... thanks for the reminder.

Really enjoyed reading this. I've got an old disco transfer box you've inspired me to rebuild. Prepare for many a beginners question

payydg said:

Really enjoyed reading this. I've got an old disco transfer box you've inspired me to rebuild. Prepare for many a beginners question

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My pleasure. Glad to have provided some entertainment. I've had a good hard thrash to Manchester and back today and the transmission temperature barely got over 100 C the whole trip. So the oil cooler (and cooler weather now we're into September) seem to be keeping things down most satisfactorily.

Brown said:

My pleasure. Glad to have provided some entertainment. I've had a good hard thrash to Manchester and back today and the transmission temperature barely got over 100 C the whole trip. So the oil cooler (and cooler weather now we're into September) seem to be keeping things down most satisfactorily.

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Question about the oil cooler. If the pump breaks are you at risk of over heating? Or without the pump are you basically back to how they are when they leave the factory?

The reason I ask is I'm tempted by the idea as mine gets used for expeditions and having the additional cooling power could be useful. Saying that if you in the middle of nowhere I wouldn't want a broken pump to mess things up.

Well, if there's a malfunction, you'd notice the temperature going up so you could just drive slowly to keep it down. Another possibility is one of the pipes coming off or a connector coming undone or some other leakage. Having said that, everything is tucked up above the level of the chassis rails and prop so probably won't get damaged even if I manage to high-centre the vehicle. And I intend to check everything for tightness reasonably regularly as it beds in. If the worst happens and the cooling system is holed beyond repair, I intend to carry a couple of blanking plugs to fit the -8 JIC connectors on the sump so I can just blank everything off, top up the EP90 and carry on as if it were a non-cooled system. The pump is the kind of thing that kit car and racing enthusiasts use on dry sump systems so it'll run long and hard (and give about 60 psi of oil pressure). However, mine isn't a high pressure system, it just needs to stir the oil through the cooler matrix because it probably wouldn't happen via convection alone.