The V8 Owners Forum -

Hi Guys,

Anyone any experience of the MT75 4x4 gearbox? Anyone know what kind of abuse power wise one of these can take and if they can be uprated to take more??

Thanks in Advance

They wont take much !!!!

They are a pretty poor box, poor shifting, and weak. Even at 350bhp ( Cossie power ) you can be on dodgy ground with hard useage.

The Swedish Fixit gearset is one option, or more recently in the UK, Marco Polo over on PassionFord has his Mullit gearset for them, which seems to be very popular.

For a decent built gearbox with stronger gears etc, you are looking at £3k

So I dare ask......what are you considering using the box with ?

Thanks for that Stevieturbo, I had been doing some searching and also came up with that figure of 350bhp. I'd of hoped for it to go a bit further without shelling out 3k.

The reason I asked about htis particlar box was they seem readily available, but if you know of any other box with the 4x4 goodness i'm listening. The project is such, I have an RV8 lump (which i'm probably going to get rid of now anyway in favour of a lexus lump) that I was going to twin turbo which I was going to put a 4x4 drive train on and then throw into a small car for hill climbs and sprints and general hooning around on the road and strip. searching on ebay came up with plenty of rangie transfer boxes but I didn't want to go that route (as I don't need the different ratios) of bolting one behind a supra box etc, I was looking for a all in one gearbox/transfer box.

So to clear up what i'm asking:

Is there an all in one 4x4 box I could use which will take big bhp(manual)?
or
Am i going to have to use a transfer box from a rangie?

Any thought and suggestions please.

In addition to the above, how tough is the rest of the drive train, in terms of the front and rear diffs?

I am not sure the RR transfer box is really what you are looking for for a "hill climb special" they are seriously heavy bits of kit and are designed to move the drive line to well below the crank centerline, though maybe that is wat you want? not sure.
A little info on where you are planning to put the engine would help, in front of the front axel line (like Audi/ scoobydoo) or transverse in the front like a golf or freelander, in the front of the car but between the axel centerlines (mt75), mid engine like a lombo or rear like a porsche. It all makes a big difference.
Mike

or even like the 6R4 with the engine behind the gearbox but with the rear diff in the back of the sump so it was notquite rear engined and not quite mid engined??
Mike

A little more project detail then, i'm looking at putting the biggest engine possible with 4x4 drive train into the smallest car possible, not decided yet on which car, theres a choice of a few, mini, saxo etc etc, you get the idea. So with regards to where the engine will be fitted, in the front for starters, and between the axle centrelines, or thats how things stand at the mo, but I am open to input on other options. I would like to go the manual box route too, whatever it is its going to be a true home brewed special.

I see what your saying about the 6r4 setup, quite simple really, surely you would need a transfer box which reverses the direction of rotation to the propshafts, otherwise your car would be seriously fast...........backwards??!! I have seen such an item on the internet before, mainly used for off road racing where the engine is in the back I believe.

Of more importance, is how you intend to implement an awd build.

transaxle ? front and rear diffs with a transfer box style ? etc etc...

MT75 is basically crap, but that depends how hard you are pushing it, and the weight of any car.
It also has an integral bellhousing, which makes life awkward.


Leaving front and rear diffs aside for a second. If you want a good value, manual gearbox, with a centre diff/transfer box built in, then just buy a Skyline gearbox.
It has an integral bellhousing too, which is a pain, but complete boxes arent that expensive, and they are fairly strong.

If you opt for a newer more expensive 6 speed variant, it has a seperate bellhousing, so that may make life easier for a swap.

If you know of anyone with a 4x4 Cossie MT75 thats knackered, give me a shout. I need a casing for one, for some butchery.

Hi
the issue of which way the propshaft's run is actually quite easy to fix (compared to the rest of the packaging), by a combination of inverting diffs (most can be turned upside down quite happily and run backwards) or swapping the crownwheel to the otherside in the case where they don't like it. You can flip the g50 porsche transaxel and run it inverted by swapping the breather and filler plugs and adding a litre of oil.
Hadn't thought of the skyline, it is a good box and includes the right center diff for what you want to do but you will need to sort out a controller for the torque split.
I think your biggest issue will be how you get drive to the front diff, it will have to be in the center at the front or you will be in torque steer territory, ask a montego turbo owner about what happens if the drive shafts are different lengths!!!
I think if you want to get this to work in somthing the size of a saxo or mini you will want the engine in the middle or you will never get the engine, transmission and front diff all in without you running along behind!
The 205 rally car (and the others of the time) had the engines where they did for a reason (actually two reason two below).
The other thing is for this to work as a nimble sprint/hillclimb car you need to keep the poler moment of inertia down, ie all the heavy bits like the engine and gearbox and diffs as close to the center of mass as possable. Achieving 45/55 weight ballance is quite easy on any set up, stick the engine in the front connect it to a torque tube and stick the gearbox behind the rear axel centerline (and stick the battery in the boot) just look at various alfas and front engined porkers, or even a C5 corvett. But they are GT cars, turn in slowley nice and stable in sweeping bends and as willing to change direction mid corner as a bus.
One solution might be a box/transaxel like the audi quatero one off an 4.2 V8, it also comes with a v8 engine attached, stick it in the middle, drive the rear wheels off the diff on the front of the box and take the drive that would normally drive the rear wheels forward and to the side of the engine, you would then have enough propshaft length to get the drive to a diff at the center of the car at the front (and be able to sit in it), you could use the box that transfers the drive forward to sort out the correct direction of rotation and use the rear audi diff at the front, the ratio wiould atleast be right. Then all you would have to do is con the onboard controller into splitting the torque in the right way
good luck
Mike

kiwicar wrote:Hi
it is a good box and includes the right center diff for what you want to do but you will need to sort out a controller for the torque split.

Easy, or hard.

CO2 cylinder, 10-12 bar will engage 4wd, or leave with no pressure, and it will be virtually 2wd. With varying levels in between.

So it wouldnt be too hard to plumb something up, either hydraulic, or pneumatic in terms of control.

There is a switch already on the box, that works whilst 1st and 2nd gear is engaged, and this engages 4wd in 1st and 2nd in its simplest form.

Or just have a manual pressure reg in-car to adjust the 4wd manually.

sorted then
Mike

Obviously this 1st and 2nd gear switch needs connected to appropriate hydraulic control solenoids and pressure to engage the 4wd !!!!

Sometimes I think I get too many ideas One R33 GTR gearbox, 5 spd manual.



Hydraulic connection at rear for 2wd/4wd operation.

The skyline box looks and sounds like a good option to me. Would it be recommended to run the front diff in the sump like on the ford 4x4 varieties? For pacakging purposes it seems like the best option, whether mid or front mounting the engine.

Whilst the audi package is an alternative, I know audis mount there engines very far forward and the gearbox for these is essentially a transaxle type, but because the engine is so far forward, driveshaft alignment isn't an issue, stick one in the middle of a car and its another matter. Am i right in this train of thought??

got a chevy and 2wd audi box in the middle of mine on a 65 inch wheel base and I can sit in it
Mike