Would this work - AWD content

So I've been doing some more planning on my dream project and then watched some grand tour about the huracan performante and it go me thinking about AWD, and I started trying to figure out a way to do homebuilt, simple, cheaper, and light awd in a mid engine car, and I've had an idea:

Take the engine and mate it to an fwd transaxle of choice, with an lsd

Turn it 90 degrees so that the engine output shaft faces forward and the transaxle output shaft faces rearwards

Remove the cv joints and somehow rig it up to propshafts instead

Connect the propshafts to the front and rear diffs

done

It seems to me like it would work brilliantly, lower center of gravity than conventional AWD, mid engine, cheaper and simpler, and all off the shelf bits, am I missing something that would make this idiotic?

Is awd really worth it?

THanks

I think a lot of off road buggies are being built this way. 

You'd have to do something creative with final drive ratios. A FWD trans has the final gearing built in. Adding more gear reductions (differentials)won't help you go fast.  The rock buggy guys do it and welcome all the extra gearing. But for road speed (wheel speed) you'd need to get creative. 

There are cheap ways to AWD though. S10 folks will often trade their 4WD transfer cases for the AWD unit found in every junkyard in North America in the Astro/Safari vans. It won't take a ton of power, and it's a bit heavy and big, but cheap and plentiful. Other ways to do it of course, but the cheap Chevy guy in me gravitates to this plan. 

In reply to barefootskater :

Ahhh I hadn't much thought of that. but it would be quite an issue, and not the easiest thing to remedy. Hmmmm

THat is cheap and easy, and quite simple......I'll look into that although the weight does make me hesitate

There's always taking a transaxle car and adding electric drive to the other two wheels. If you start with something that has both FWD and AWD models, start with the AWD one, grab an FWD trans to swap in, and then bolt a large electric motor to the input of the rear diff. Unfortunately nothing 'supercar' cool comes standard in both FWD and AWD configurations.  Plus you're starting with a car that is already AWD. Could be a really neat setup to do front motors on a 911, but wouldn't be a "budget" build.

Or, subaru/audi transaxles. 

I think you can get quickchange differentials configured to nearly 1:1, but they aren't cheap and I'm not sure if you can run them as IRS.

Another option would be to use chain (or belt) drive differentials, but then you've got the long chains to worry about and convert the output of the transaxle to chain drive.

I remember watching a Junkyard Wars episode where someone did this and it had a top speed of about 10, but it climbed the hill quite well.  The lack of suspension on their build hurt them ultimately, but if they had some articulation it would have dominated the competition.

I wonder if those shows are available online?  That was a fun series to watch.

Robbie (Forum Supporter) said:

There's always taking a transaxle car and adding electric drive to the other two wheels. If you start with something that has both FWD and AWD models, start with the AWD one, grab an FWD trans to swap in, and then bolt a large electric motor to the input of the rear diff. Unfortunately nothing 'supercar' cool comes standard in both FWD and AWD configurations.  Plus you're starting with a car that is already AWD. Could be a really neat setup to do front motors on a 911, but wouldn't be a "budget" build.

Or, subaru/audi transaxles. 

I kinda want to do this with my 924.  Use MK1 Golf front uprights and add motors to each assembly.  Load the rear with battery pack(s).  Add higher rate springs and dampers all around.  Would probably need wheel speed sensors at each corner and a way to control the motor speeds.

Just do what the Deep Sanderson did - have an engine/transaxle unit at each end of the car (in that case, old Mini). Just make sure that you get matching throttle settings, though - wouldn't want one end out-accelerating the other....

In reply to wspohn :

This cavalier showed up at a Bethlehem PA "Cars & Coffee" set up with two complete engine/ transaxle packages installed. Not especially light weight.

What about planetary hubs from, say, an older, small farm implement or construction equipment and add that to the outputs from the trans? But in reverse.  So instead of gear reduction,  you get gear multiplication. 

Some Haldex units have a 1.2:1 ish final drive, keep the major gear reduction in the transmission.  Not terribly strong and limited slips are scarce.

GM automatic transmissions have a PLANETARY final drive.  This means with some creative machining and welding, you can make it 1:1 and use normal differentials.

Hot Rod TV did a Impala SS (V8) and put a Pontiac GXP (V8) in the rear.  Lots of fab work but it is a screamer.  = AWD

In reply to Robbie (Forum Supporter) :

Yeah I've been trying to think about it for a sort of scratch build I'm working on planning for, it doesn't really have front diffs

In reply to Stefan (Forum Supporter) :

The issue with chains is lubrication and longevity, they are very easy to have crap out on you etc

In reply to Stefan (Forum Supporter) :

Oh lord that would be glorious, do it do it do it

In reply to wspohn :

yes but that's impractical and heavy and finicky etc

In reply to TurnerX19 :

It's cool and all but heavy and such setups are usually finicky and iffy and unreliable

In reply to Appleseed :

that might work......

In reply to Pete. (l33t FS) :

no slushboxes for me!!

I'll look at the haldex units

In reply to 68TR250 :

thanks, I'll look it up. Probably heavy though

It seems like it might have weird left/right weight distribution because the motor is presumably going to wind up being offset to one side?

Given the preponderance of AWD in mundane vehicles these days, I wonder what sort of transaxle/transfer arrangements are littering the junkyards?

Aren't a bunch of AWD BMWs configured with the front drive basically running right through a notch or even a hole in the oil pan to a separate diff up front? Seems like an easy way to go mid-engine, as the only thing that would need to change is the lengths of the front and rear driveshafts. Of course, all but the oldest probably need the BMW computer to run the center diff clutch...

I guess my thought here would be, what's the purpose of the car?  If it's pavement, AWD doesn't really have a lot of advantages.  If it's for gravel, the mid engine layout doesn't really have a whole lot of advantage.  On that though, i think the neatest awd mid car I've seen was Andy Burton's 306r4.  If i remember correctly, mid engine, with it turned backwards, transmission facing forward, t-case running drive shafts for and aft, independent front suspension, DeDion in the back. 

That guy's a freakin genius. 

In reply to codrus (Forum Supporter) :

Yes that is true, but I'm wondering if it will be enough to actually affect it

In reply to Jesse Ransom :

I actually don't know, I know plenty of awd cars do that, for example the r8, but I'm not sure which BMWs do, and how to configure it mid engine