So: This thread will cover the rebuild and engine conversion of my 1985 127 Double Cab.
The engine I've chosen is a Mercedes-Benz OM606 - 3.0 TD from a 1999 E300. I will also be installing the Mercedes 5 speed 722.6 automatic '5G-Tronic' gearbox as well.

So this is how it began:

As bought. The truck is an early 127" model, which were all built from 110 chassis' by Land Rover SV.
Its first owner was the Southern Electricity Board, and it would have originally looked a bit like this, as a 3.5 Rover V8 with LT95 4-spd transmission.



After its service as a utility truck with SEB, it was then bought by a youth club-cum-scouts group down in Southampton, who rebuilt it onto a Richards galvanised chassis, painted it red and yellow, added stripes and decals all over it and added lots of modifications and extras.

In its time with this owner, the truck traveled all over the world, taking many intrepid explorers and young scouts with it! The list of places it went over the years is quite astounding, but off the top of my head:
- USA - Nevada, Texas, California etc - around 5 separate trips.
- Sweden
- Norway
- All over North Africa and the Sahara
- etc. etc. etc.

Here is one of many articles that it has been featured in. I've got 3 so far but am aware of a few others.




So anyway - off we went with my brother's 90 and a hired trailer to go and collect it from sunny Southampton.



All was going swimmingly. For about 10 miles. At this point, fate, inexperience and a badly loaded trailer conspired against us and this happened:



Could have been much worse. In fact it was probably the slowest car crash you've ever seen. Travelling at about 25 mph down a slight hill, the 'tail started to wag the dog' and we ended up crossing the wrong side of the road and taking out a roadside fence, in the process writing off the drawbar of the trailer and damaging the 90. Again, it could have been much worse. As it was, it was a double recovery job for the AA, a smashed trailer and a squashed ego.



That's all for now.. the story will be continued shortly!

As a general rule of thumb - if the trailer + load is bigger and heavier than the tow vehicle.............................. that's what happens! [unless it's an artic] Very jealous of the project though [you don't happen to have an o/drive going spare do you?]
good luck

Looking forward to the next installment!

As soon as I read 'my brothers 90' I thought 'that sounds dicey'. Then j scrolled down. Lucky escape. Looking very forward to reading through this thread. Om606 has been on my mind for some time but will have to wait until I've got more space. Are you converting it to om603 inj pump? Is that gearbox you mention heavily dependant on electrics?

Now a little more detail about the powertrain I've chosen and how I came to the decision.

The OM606 (specifically, OM606.962) is a 3.0, straight 6, 24 valve motor which produced from the factory, 174bhp @ 4400rpm and 243 lb/ft @ 1600rpm and was fitted to the E, S and G class Mercedes of the mid to late 90s.



Whilst it may seem to be a fairly innocuous lump at first glance, it is a monster in sheep's clothing.
Somebody way back down the line somehow discovered that these engines are good for 500+ bhp without touching any of the internals - by just adding a beefy injection pump and turbo.

Whilst my power goal of 250-300bhp is nowhere close to that figure, it is nice to know that the engine is proven and durable at much higher power levels. Mine came from a 1999 E300 TD - and even in completely stock set-up, it was a very brisk and responsive drive, so with an extra 100bhp and an extra 200 lb/ft or so, it should push the 127 along nicely! To achieve this, I'll be giving a diesel injection specialist by the name of 'Dieselmeken' lots of money for one of his 'super pumps'. For now I will stick with the stock turbocharger, but I am researching a suitable upgrade in the future once I hit the limits of the standard one.

Initially I had considered the Cummins 6BT conversion (now becoming quite common), as I was attracted by the huge torque and simplicity of the engine. However, I chose the OM606 over it for a few key reasons:

- NVH and refinement - being a truck engine, the 6BT is loud. Very loud! Not only that, but vibration is also an issue. On the other hand, the OM606 was the most refined diesel engine of its day, as you would expect from a Mercedes saloon car. With some good soundproofing and careful choice of mountings, it should be a very refined drive (for a Defender!).

- Weight - at around 500kg, the 6BT is twice the weight of a Tdi - and that's before you add the extra weight of the truck gearbox you must run behind it. That much weight over my front axle didn't seem like a good idea, particularly as I want to run a front winch and bumper. The 606 on the other hand weighs around 260kg. I believe the gearbox is lighter than an LT77, so overall weight should pretty well match that of a standard Tdi.

- Lack of a good/feasible automatic gearbox option - whilst there are a couple of Allison automatic
gearbox models designed to work with the 6BT, they are very large and heavy, and not all that easy to obtain in the UK. The 606 comes bolted right to a strong, modern and smooth 5 speed automatic transmission.

Of course, being double the displacement, the 6BT produces far more torque within a much lower rev range than the OM606 could - but I believe the 606 will be more than adequate, and has a much wider useable power band (6000rpm redline) than the 6BT.

The transmission I am using is from the same car, and is called the 722.6 5G-Tronic. In E300 TD form, it is rated for approximately 380n/m of input torque (50nm more than standard OM606 output), but has been proven to be reliable at much higher torque levels. There are other, beefier variants of the 722.6 available that were fitted to V8 and AMG models which are rated to more than double this.



Being electronically controlled, I'll be using Ole Fejer's ECU which he has designed and built from the ground up. This will allow massive customization of the gearbox characteristics, as well as speed/pressure/temperature readouts etc. Very cool stuff.

Should be lively

Great stuff. Even Jeremy clarkson admired this engine way back in the late 90's, and he publicly hated diesels until very recently. Any clues as to the cost of the fuel pump and the gearbox ECU? I've read about the use of manual 6 speed boxes from sprinters or vitos, and BMW gearboxes, but it's usually speculation - never 'I've tried this and it actually worked and has done for this long' type of comment.

fascinating project... watching with interest.

Discokids said:

Great stuff. Even Jeremy clarkson admired this engine way back in the late 90's, and he publicly hated diesels until very recently. Any clues as to the cost of the fuel pump and the gearbox ECU? I've read about the use of manual 6 speed boxes from sprinters or vitos, and BMW gearboxes, but it's usually speculation - never 'I've tried this and it actually worked and has done for this long' type of comment.

Click to expand...

Correct I believe this is the review you are referring to...



Fuel pump and ECU are the biggest costs of this entire build. Fuel pump is around £900 built to my specifications, and around £500 for the gearbox controller with an OLED readout and everything required to 'plug and play'.

Yes I have seen some use of that 6 speed box. Would have considered it but I really want a smooth auto.

Yes, that's the one. I just didn't know how to link it as I'm not up on this internet lark. Considering a running e300 can be bought for as little as £300, £1500 for those two bits probably isn't that bad if you want a big power engine In a large vehicle and dont want to change gear.

What's the gearbox controller, megashift?

Discokids said:

Yes, that's the one. I just didn't know how to link it as I'm not up on this internet lark. Considering a running e300 can be bought for as little as £300, £1500 for those two bits probably isn't that bad if you want a big power engine In a large vehicle and dont want to change gear.

Click to expand...

My engine and gearbox were effectively 'free' from my father's old E300 DT. It had done only 100,000 miles and had main dealer service history from new but like many Mercs of that era, succumbed to tin worm and was condemned.
And precisely my thoughts - even a Td5 conversion would wind up costing much more and would not provide anything like the power, torque or durability that this promises.

Bennehboy said:

What's the gearbox controller, megashift?

Click to expand...

Ole Fejer's 722.6 controller. Info can be found here: http://www.ofgear.dk/

Watched thread you bugger, you really know how to grab somebody's attention sir!

Watching here also. One for future reference.

Very interesting thread.

Will this connect to the transfer box ok?

Love those big trucks. Watching with interest!!

There was a feature in Lro last July I think it was about a guy that had done this engine conversion. it had lots of good information.

The interesting bit will be attaching the gearbox to a Land Rover transfer case, if that's the way you're going. There'll be some challenging machining of adapter plates and adapter shafts to do.

I've seen it done using a very short propshaft, about 7-8" iirc. God knows how far back the transfer case would end up although in a 130 who cares??? I've wanted to do this myself for ages with an RRC. And just running it (please don't insult me) RWD.

I know a chap who's doing this conversion on a D2, he's divorced the transfer case and is using a short custom prop.