4x4s with independent front suspension & non-offset diff?

[rcx106]

I'm looking to build a custom trials/challenge vehicle and looking at drivetrains. I'm looking at solid axle on the rear and independent front suspension. But I want the front diff to be centred, whereas most 4x4s with independent front suspension have the diff slightly to the side, and not in the centre. This limits the length of the suspension arms and hence limits travel.

I could have the front axle case modified to make it symetrical and centred but then I'd still need need a matching rear axle with same ratio, or one of the propshafts will need to operate thru two angles which means I can't use a double cardon propshaft. I could live with this, but worth seeing if I can find a better solution.

Also, the diffs would need to have lockers available such as Kam lockers or ARB lockers, which limits my choices. And decent availability of gear ratio modifications either in the diffs or transferbox.

The transferbox/gearbox and axles don't need to be from the same car. So, basically, I'm looking for a matching rear solid axle, front independent axle which is not offset. And a transmission with transfer-box which also has centred output shafts.

I know there's specialist solutions for this but I can't afford them, so need to be from a production vehicle. If possible that is. Otherwise I'll just have to compromise somewhere.

[GravelBen]

Subarus have independent suspension and non-offset diffs, but you probably want more travel than that!

(I'm sure someone else will be along with a more useful answer shortly)

[rcx106]

Thanks. Actually I'd only be taking the drivetrain from the donor cars. I could even take axles from one car and transmission from another. So travel would not be affected by the donor vehicle.

Suburu has independent rear. That's a compromise I could live with.

Would still need a transmission with centred output shafts and Suburu doesn't have a transfer box. Again I could live with that though not ideal. I was going to try to road register the car, dunno if that's easily possible these days, for some road fun as well, but that would need transfer box to switch between low and high ratio.

[GravelBen]

Some Subarus do have dual range boxes actually - manual Outbacks, Foresters, old Leones, even some of the previous NA Legacy models.

The low range in the newer ones isn't overly low, but the older ones are pretty good.

May not help you with wanting difflocks, but plenty of them have rear LSD if that helps. Not sure about different ratio options, or how long they would stand up to trials abuse - they're fine for rallying, but I imagine that big tyres would add a fair bit more load.

Edited by GravelBen on Saturday 31st January 11:12

[Konan]

Tricky, this one! I'm struggling to think of anything common that outputs drive to the front in line.

If you use another transmission with the Subaru setup you're going to loose the front diff; it's part of the gearbox. I don't think Subaru diffs would last very long in off road trials.

Everything I can think of with a transfer case (integrated or separate) has the front prop offset to avoid the engine sump. The only thing I can think of is if you had the engine high enough / dry sump you might be able to rotate a transfer case and run the prop under the motor. I suppose the good part here is that since you're not using a live axel the diff will be fixed so the prop won't need to move up when the front suspension is compressed.

You'd still need to find something with the front diff in the centre. I wonder if it's possible to chop about a couple of MK3 shoguns. They're independent sus all round, but it might be possible to fabricate something that allows you to use a rear diff/props up the front end?

[TooMany2cvs]

Problem is going to be that anything with a separate front diff, rather than a transaxle, is very likely to have it offset - purely because the alternative would be to have the engine and box offset, so that the transfer box output can be central and miss the sump. Big packaging compromise to get round something that's a bit of a non-issue.

Your best bet would probably be to look at a RWD drive diff and mate that to custom driveshafts with CVs at the outers?

[rcx106]

I found the Freelander which has a centred drivetrain and independent suspension. But there are no lockers available for it :/

Ah yeah, a Suburu would have the front diff in the gearbox. So that won't work. Ok I see now why the front diff is offset to avoid the sump, didn't think of that. I've started going thru all the cars that ARB supply lockers for to see if any have the centred driveline and independent suspension or IFS.

[normalbloke]

H1 Humvee.

[TooMany2cvs]

rcx106 said:

I found the Freelander which has a centred drivetrain and independent suspension.

Another transaxle, though - and one with a transverse engine, too, so not particularly centred.

[rcx106]

TooMany2cvs said:

Another transaxle, though - and one with a transverse engine, too, so not particularly centred.

K. It looks like I might be asking too much! I've found this company and their tech article which explains most things: http://www.proformance.com.au/#!ULTIMATE-IFS-WHEEL...

They are saying that most teams get the narrow diff by making or buying an aftermarket axle case and using a regular diff inside. But no word on how the prop shaft then needs to run diagnally or what in these home made solutions.

The same company produces an "underdrive" transfer box which lowers the output to clear the sump, so that solves things. They have all the solutions but prices are well out of my range.

So I either have to stick to solid axles or live with the shorter suspension control arms and limited travel.

[TooMany2cvs]

rcx106 said:

But no word on how the prop shaft then needs to run diagnally or what in these home made solutions.

What sort of layout are you going for?

If it's a front/front-mid engine single-seater, you could offset the engine/box, so the transfer box output's roughly central.
If it's a longitudinal rear-mid, then you've got plenty of space for the front to be straighter, especially if you turn the whole drivetrain 180, so that the flywheel's at the front of the engine.

If the rear's a solid axle anyway, then that's less important whether that's central or not.

[rcx106]

I only briefly considered a rear engine layout, partly because not many others are doing this, but also doesn't it mean that the diffs then need to run upside down and I don't like that kind of bodging.

Yes I can offset the engine. It's all about compromises hey! This may be the route to take; modified axles to centre the diff, and offset the engine.

[PugwasHDJ80]

The idffs con't have to run upside down

an LT230 can input power through the ouput side of the transfer case which automatically reverses the engine back to the "right" way for the diffs.

Couple of places also do reversing 1:1 gearboxes for exactly this problem

[rcx106]

PugwasHDJ80 said:

The idffs con't have to run upside down
an LT230 can input power through the ouput side of the transfer case which automatically reverses the engine back to the "right" way for the diffs.
Couple of places also do reversing 1:1 gearboxes for exactly this problem

Sweet, I'm getting better tips here than on Pirate4x4!

[PugwasHDJ80]

You'lll always struggle with pirate because they can get "better" stuff than us

An atlas T-Case with Dana 60s, or Ford 9"s will do exactly what you want, cost about 20p in the states but will cost a fortune here!

One of the best drivetrains I've come across for light off road custom build buggies are Vitara setups- can take lots of power. No idea if the diff is offset though.

To be fair if you are building custom wishbones wouldn't it be worth making custom half shafts?

the very best build I've seen from a totally custome made perspective is from Simon Rafferty the guy who started and designed all the bits of X-eng. Si is a total genius!

http://forum.difflock.com/viewtopic.php?p=15229

[TooMany2cvs]

PugwasHDJ80 said:

One of the best drivetrains I've come across for light off road custom build buggies are Vitara setups- can take lots of power. No idea if the diff is offset though.

[rcx106]

I know the Vitara very well, off by heart in fact. I know it's super light but it's a 100 bhp car with 27" tyres. It won't take the planned 300 bhp, 35" tyres, and planned abuse. I was thinking something like a Hilux or similar size/spec/strength. Half shafts should be easy to make. Rockwatt in Lincs modifies them for nice and cheap prices.

At the moment I'm thinking that to offset the engine is not a bad idea, or live with the shorter control arms or combo of both. I'm making the car quite wide for stability so that will also add suspension travel.

[PugwasHDJ80]

if you want that sort of abuse (the tyre size sounds like the biggest problem), then you're probably wise to lookin into Landcruiser Colorados- they will certainly take a fair pounding. nothing like an 80 series but their are upgrades out there.

[rcx106]

Figuring out how strong the drivetrain needs to be is not going to be easy. I think that can only be figured out from experience and speaking to people who have experience. The Landcruiser is heavy and I'm trying to keep weight low. I was hoping something like a Hilux drivetrain would be strong enough, it's not too heavy, it's cheap, there's wide range of gear ratio mods available for it, and lockers are available.

From what I hear it's the axles that gives way a lot more often than transmission or tbox.

[TooMany2cvs]

rcx106 said:

From what I hear it's the axles that gives way a lot more often than transmission or tbox.

Don't forget that you really do want some kind of a known weak link - something cheap and easy and quick to replace - to act as a "fuse".