Searching for AWD/4WD System

[NolimitZ32]

Hey all, I won't go into details just yet but I am looking for some suggestions of AWD or 4WD systems (mainly the t-case or center diff) which meets the following criteria:

1. Utilizes a separate front differential (porsche, subaru, DSM are out).
2. Is a 50/50 (under normal operation) mechanical/clutch/viscous torque split system or one that has the potential to be controllable to send any amount to either axle. (Haldex type)
3. A huge plus would be if the system in whole or just the t-case/center diff are readily available stateside.

This would be used to assemble an on-road full-time AWD system for a little project I am hoping to build sometime in the not to distant future and would really appreciate your help on this.

Thanks guys and gals.

[Looneybomber]

2. Is a fixed 50/50 torque split system has the potential to be controllable to send any amount to either axle. (Haldex type)
3. Contains a viscous coupling or center diff.

So it sounds like you DON'T want a fixed 50/50 because otherwise you would not need it to be controllable or have a viscous or clutch center diff.

That said, you said Subaru was out because they don't have a front diff? I assume you are looking for a separate unit than the transmission/gearbox/diff combo that WRX's have. So are you looking for a truck like setup where the transmission mates to a transfer case, which then powers drive shafts to front and rear axles/diffs?

[NolimitZ32]

I edited the first post to hopefully explain a bit better. Perhaps fixed isn't the right way to say it. I do want a 50/50 split (under normal conditions), I realize that once the viscous coupling or center diff and wheel slippage is introduced its no longer 50/50 but will distribute torque as it should, the need for the viscous coupling or open/lsd center diff comes from the fact that most off road t-cases are locked between the front and rear shaft (and are fixed/locked 50/50). If not than I want it to be fully controllable. I realize that one is far from the other in every aspect but I can't explain any further without going into detail about my plans and for the sake of not looking like a useless dreamer if things don't work out I'd rather keep it to myself for now.

So yes I want a system which physically is like a truck or pre-R35 GT-R, comes in 3 pieces: 2 diffs and a t-case or center diff. Which will operate on pavement as an AWD without drive-ability issues. And is available Stateside.

[alms24sebring]

Is there a reason why you want a separate front diff? I guessing because of the axle angle would be too far back with a transaxle. What about something from a Jeep? Custom mounting plates to make it work.

[MinisterofDOOM]

You want 50/50 during normal driving...is there a time you DON'T want 50/50? Are you wanting more to the front, or the rear in those cases?

Seems like a slightly odd combination of attributes for an AWD system.

Most car-based AWD systems with a separate T-case and front diff will NOT be 50/50 most of the time (they tend to be rear-biased with the ability to shift power frontward).
Most truck-based 4WD systems will have a separate t-case and diffs at both ends. Truck t-cases are heavy, though, and are usually dual-speed.

Pre-R35 ATTESA AWD was available on some US models. Notably the G35 and M35, as well as the EX35. It's probably the closest thing to what you're looking for, except that ATTESA shoots for 20:80 or even more aggressively rear-biased power split in normal driving.

I guess the big question is: are you looking for a 4WD (offroad) system, or an AWD (passenger car/onroad) system? They tend to be very different beasts.

[NolimitZ32]

Alms: I want a separate front diff because of the physical location of the engine in comparison to the diff. I've actually been looking at Samurai t-cases, fairly small & lightweight.

MOD: As I said I can't say more without really going into detail of what I want the end product to be (and at this point I don't really want to). What I want is something that will be 50/50 under normal driving conditions as in straight line dry pavement. Obviously the system will decide how much torques goes to each axle under not normal conditions. And as I said above its got to be a full time AWD system for pavement so no locked diffs. I realize it seems like an odd combination but just humor me. And just so we are all clear (not meaning to sound like a Richardhead) I'm an engineer and am well versed in many things mechanical/automotive. I don't need an explanation of HOW things work I made this thread because I surely don't know of every vehicle ever that was made with a AWD or 4WD system and would like just some suggestions of vehicles to research. I've researched the BW4472 (Typhoon, Bravado, Safari), the Sami, the TX-10 (WD/D-21), the T-100 (Datsun 720) and a few others. So far the BW4472 looks to be almost what I need (except the torques split is 35/65). Thanks all for your help, any and all advice and constructive criticism are greatly appreciated.

[MinisterofDOOM]

And just so we are all clear (not meaning to sound like a Richardhead) I'm an engineer and am well versed in many things mechanical/automotive.

D'oh. I fail. No condescension intended.

I've researched the BW4472 (Typhoon, Bravado, Safari), the Sami, the TX-10 (WD/D-21), the T-100 (Datsun 720) and a few others. So far the BW4472 looks to be almost what I need (except the torques split is 35/65).

There's a really good point. I completely overlooked the fact that there are a lot of more "luxury" or street-oriented TRUCK systems that are really AWD vs 4WD.

Here's a neat PDF I found documenting the specs of GM's various truck t-cases, including single-speed full-time AWD models. Seems like most of them are not 50/50, and I'm not sure how easy it'd be to change that split with planetary differentials. I know the Silverado SS's t-case was more like 40/60.

Ford also used a more "carlike" AWD system in the Navigator and Aviator. But those were 35/65 split. I'm a bit more familiar with these due to my research into AdvanceTrac (which is a component of certain AWD setups on Ford trucks). They're not as beefy as GM's...not intended for as much "real truck" use and more purposed for mallhopping SUV duties and getting Jesda stuck on snowy shoulders.

[NolimitZ32]

MOD you are the MAN! I didn't even think to look at more recent GM and FORD, for some reason I did look at Chrysler though. Thanks man, everyone else, please keep em coming.