Thread: Theoretical exercise RRC engine swap

Originally Posted by loanrangie

Yeah not a fave of mine either, if the 722 was fitted to a 4wd then possibly one might have a suitable flange.

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yes, the 722.3 & 722.6 variants fitted to w460 & w463 Gelandewagen. also w461 g-professional & other steyr-puch creations using MB engines.

in all cases the t-case is divorced from the transmission.

for me it's more a question of maximising the efficiencies that can be gained via using the 722.6 5 speed unit, as opposed to a 4 speed.
yes it's added complexity. Some electronics, albeit a standalone fully-programmable shift controller - I'm not disagreeing on your point. the 722.6 was used reliably behind the 6.5L v12 biturbo amg, so it can handle the torque of a boosted OM606 or tuned m117 easily enough, and it's a bolt-up solution.

The secondary point of this exercise is to continue researching what will definitely not work post transmission - / what will break / what will be borderline in terms of driveline components.

I'll obviously have to ditch the BW in favour of the LT230. That much is a given, considering all the advice I have read here and elsewhere. Which is a bit of a shame, because I find that the BW as it is in this vehicle now to be very nice and smooth.
Apparently the 4HP22 isn't real strong in the torque dept either. so mating that to a turbo 606 possibly not the best idea, yet it may be able to take the 450Nm from the m117.

I do not know if the LT230 case would benefit from an ATB centre, but I would probably buy one in this configuration from ashcroft etc with the ATB centre already fitted, since I'm likely to have to ditch the BW anyway.
I don't like uni joints, and much prefer CV's, so there are some changes I'd make in the propshaft dept. This would be beneficial overall, especially if I have to divorce the case or use a VG80 or 150 - again, not ideal, but I have to process the requirements before I can analyze the costs and see if it is really worth it.

Then diff/axles/hubs.... again, there are too many options people bandy about - so I have no ****** idea what the best and most cost effective reliable option for an RRC is, be it wholesale axle housing removal or complete swapping of all internals, or simply remove and replace 'some' subcomponents to achieve greatness. I don't know if 24, 30, 33 or 35 splines are required, or even if they are worth the claims. I do know a little bit about axles, having snapped plenty of them in the past, but not in a 4x4.

The big issue is the longterm goal. Right now, it's a bit too vague, so I am trying to simply eliminate ideas on purely a 'cost vs benefit' basis.

I may never again even consider further modifications or additional repowering if I go OM606 and get it 'right'. But there are a couple of things in my way, one of them being this lovely v8 and supercharger and gearbox combination I happen to have sitting here.
The other thing in my way is wanting to do something more or less 'cosmetic' - and that is a larger wheel/tyre combination, without making the vehicle a pig to drive or uglier than a hat full of you know whats..

I think the diesel option is more intelligent, but the petrol more powerful (and better sounding).
The idea of 35" Claws under the arches has always appealed to me. Getting the suspension setup to achieve this in an RRC seems to be overly complicated compared to other vehicles. Or perhaps I have simply read too much.

Then there is the issue of combatting the extra drivetrain stress with the larger tyres.... tougher axles, diff ratio changes possible, fine spline hubs.... I really don't know enough about LR parts or specs to understand fully what will be OK as an interim measure or if the full-scale big dollar upgrades are required just to make a basic wheel diameter change..

This is one area where I obviously understand mercedes-land much better. I could tell you knowingly that a pair of gwagen axle assemblies are near enough to bulletproof, and to fit 35's no performance mods would be required other than ensuring everything is serviceable - and if it's not, then it's simply a case of overhauling/greasing the bearings/seals/swivels etc and get back on the road again.

But this is not a G, and I'm glad it isn't in many respects.

I think my biggest issue is that I have with planning it all, is that I see all you guys modding the monkeys out of your 110's 90's & 130's and discos and I get 4x4 envy. I'd love the RRC to be able to cross axle 90 degrees, but know it just isn't meant to be for me, yet part of me wants that articulation.


Yes, 35" tyres would be a desirable outcome, as would more torque.

if the 4HP22 could reliably live behind a 455NM 220kW 6500rpm screaming OHC mercedes v8, then all I'd worry about is the bellhousing adapter & the $2K pricetag for a custom torque converter to make it all fit and work properly.

If I must upgrade axles / diffs / hubs / cv's etc to make a set of 35's work, then I really need to cost it out in detail. It's probably the biggest modification to the vehicle I'll be making, so I want to get it right.

The engine stuff.... well the 3.9 is still in there plodding away right now, so I have time on my side to get all the extra details thoroughly sorted before embarking on the swap. It's only really the transmission / transfer case decision that will influence the engine choice. That will simply come down to costing the two options out in detail... which I've already started.

No hope of an lr zf lasting with anything more than a mild 4.6 ,shame about the divorced 722 but if it has a removable extension housing anything is possible.

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The rear housing on 722.3/4/5 units contains the govenor and speedo drive / hall sensor ring, and rear bearing.
the 722.6 has a much more condensed rear flange, however, it simply means less room to work with, as all the same stuff is crammed into a tighter space, with electrics. The main issue with that is the 722.6 actually has a longer case than the 3/4/5's. so while the rear housing is super short, the case grew in length to support all the internal stuff.

I'm not sure if any of the diesel guys out there have ever seen black smoke racing, but basically for the last 5 years they have campaigned various mb diesels in a w123 TE drift car, then later into other vehicles. The 123 was/is arguably their most famous car and they currently run an OM606 with about 7-800bhp. yes.... it's a bit mental. but behind it sits a 722.6 from the v12 mercedes and minimal internal modifications (extra clutches) and holds together well.

I had another conversation with the torque converter guys, and gave them some accurate figures from the last engine dyno sheet I had for the m117 and then factory om606 figures.
His response was 'marginal reliability behind the v8' and 'don't bother with it behind the diesel, use the benz tranny, it's f-ing bulletproof'

So now it's back to the drawing board, and time to examine how to fit an OM606/603a/722.6 hybrid and a divorced LT230 with ATB centre. I haven't thought to ask Dave Ashcroft yet about the acceptable torque ratings of one of his transfer cases, I'm sure he gets emails and phonecalls by hundreds of people about the same thing every day.

LT230 is strongest trans made by LR and will survive with only a little acceptable backlash at worst, divorced may present issues with the rear shaft but depends how much space you need.

This may open up some options -

722.6 Transmission For Sale

http://www.rakeway.co.uk/page12.html

Merc..........

You might find this thread on Pirate interesting........

Slammin's RRC.... - Pirate4x4.Com : 4x4 and Off-Road Forum

The way they are thinking opens up all sorts of options, go to the end haha.

cheers, DL

How will you go with length if divorced?