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The issue with doing this on a budget is that you will be using OEM parts. And AFAIK there is no OEM center diff that can be turned around to give rear bias. Your choices are either run a front bias system or a locked system. And if you run a locked system, then your f-r brake bias is negated and every time you pull the handbrake all four tires lock up.

if good understant cheapracer, similar to skyline r36 (not trasfer box in rear, but all gearbox)


ford rs200 in rear engine

subaru libero rear engine


gearbox from audi,

http://auto-lib.ru/?p=334

Lamborghini simply run a vicious LSD to the front diff on all their AWD's (and VW do it on the way to their rear diffs) - you don't actually need a center diff.

I hypothesize that an overrunning sprag clutch with a shorter front diff ratio would do it to but have never tried it - but DP Cars is about to so will see how that turns out for them (front drive freewheels unless wheel'spinning rears catch up).

Anyway, bottom line is I would prefer a powerful car with 4WD than 2WD if can't have AWD.



Nope, but you need individual handbrakes to lock up the outside rear only - you forgot cars have diffs.

I'm speaking from experience here. I built and crew a Subaru rally car with a welded center diff. The handbrake locks up all four wheels. The rears through the brakes and the fronts through the drivetrain.

Honda did something similiar with the RAV4. .. a FWD vehicle with a locked transfer case and a viscous coupler on the rear diff pinion shaft.
If the front tires (and therefore the driveshaft) get going faster than the pinion shaft it starts to engage and power the rear wheels. You could use the same concept in the front.
Sure would be a lot easier to fit if you tilted the engine.

Had the idea to viscous coupling. Use honda pasport (usa model if good remember, 4x4 offroad vehicle) gearbox. Gearbox have front/rear 0/100% front/rear, or 50/50% center lock. Center lock is bad on hard surface, so on the front driveshaft put viscous coupling. When they want to have fun can use RWD or 4WD

Honda Passport = Isuzu Rodeo. Badge engineering. ..

Read my post again.

This is a typical Lamborghini front diff, the viscous coupling is in that bulge (red arrow) - easy hey, so off you go to the local car wreckers, should be plenty laying around for surely no more than $100 ....

but need two, one stock, one remove viscous coupling (same diff ratio front and rear)

Close enough would be fine I think preferably with a slightly shorter rear ratio. I don't know how far apart the ratios could be before heat in the viscous coupling constantly slipping starts to be an issue.

But a bit irrelevant in a 'lo(w)cost' arena anyway.

I'll be watching too. I've thought much the same thing.

My guess is that under some circumstances there'd be a noticeable thump as the sprag locked. There might also be some odd steering wheel twitches when rocking the throttle in a corner. The OEMs want to avoid customer complaints but it would be no problem for me.



I don't even require "powerful" to any large degree. The closer you push a 2wd car to the edge of the traction circle, the more it closely resembles a ballistic missile than a guided vehicle. 4wd lets you change the car's yaw angle and apply power whether it's steering or sliding; the edge of the circle changes from a sharp limit to a fuzzy range where you can do things a 2wd driver can only gawk at. More power just lets you do it at lower speeds.

"That car looks like a cat on a slippery floor when it makes a turn..."

I'm sure ya'll remember the 4wd spitfire pic's I posted. ..
Here's a little something for your entertainment along similiar lines. (little )

http://www.youtube.com/watch?NR=1&v=MDU5BU_qSJU

I have a question about this setup. In a standard inline front engine layout the prop shaft to the rear diff turns clockwise facing it from the front of the car, does the prop shaft to the front diff turn clockwise as well? If so if one was to use the layout listed above the drive shaft would now rotate counterclockwise facing from the front of the car, correct? If one was to swap the diffs, that is put what would normally be the front diff to the rear, which rotates counterclockwise in it's normal orientation when facing from the prop shaft input, and rear to the front, which would now be rotating counterclockwise when facing it from the front of the car but would also be turning clockwise when facing from prop shaft input, it's normal direction, wouldn't the need to turn both diffs upside down no longer be necessary to get the proper wheel rotation?
This is confusing and a bit of a brain teaser for me without having a diff in front of me to figure it all out and if one would end up with "more forward gears than reverse"

Ummmm, hmmm.
The easiest visualization I can think of is to imagine just the pinion and ring gear interaction (I use my hands).

Viewed from the front of the vehicle (front engine rear drive).
shaft outputs are all clockwise, the pinion is on the left side of the ring gear in the rear.
Since the diff is rotated on the horizontal plane (left axle becomes right axle etc) to fit in the front, the pinion is now on the right side of the ring gear and the shaft rotation matches up to the desired axle rotation.

So, if you reverse the output of the shafts by rotating the engine on the same horizontal plane then you would have to reverse the output of each diff to match.

Simplest way to do that is to flip the diff, most diff cases are assymetrical so you can't just flip the gears inside the case.
The problem becomes oiling since the ring gear is now throwing oil at the bottom of the pinion instead of the top where it can dribble down into the pinion bearing. ..