Is AWD mechanical socialism?

[olason]

What parts are you going for and from what company/brand for a smart AWD setup. I know RSGear has an adapter to a syclone transfer case from a T-56 with the Corvette transaxle t-56 adapter. It is a dumb system as it is all set by the viscous coupler. I am looking at this setup in an AWD Oldsmobile 442, as I don't have all the corners and super rough roads, but I have snow a majority of the year. Which in fact we still don't have any in Fargo, ND right now.



I have a trailblazer ss and it does alright, but its AWD setup has its own problems. I like how the GT-R uses all the computers for control, but is there any tuner or aftermarket company who could help in taking all the inputs and telling the AWD setup how to act like in the GT-R.

I also like the layout of the GT-R, other than the fact of 2 full-length drive shafts. The transmission/transfercase being attached to the rear axle really places a lot of the mid-car drivetrain weight with AWD at the rear of the car where it can help with traction. The front already has the engine for weight.

[Kenny]

I will be using the '99 up Astro/Safari or a '07 up GM brain. Supposedly the Astro is a standalone. The front can be completely locked out, full locked 4x4, or auto engage with a switch. The default settings would probably be perfect for your application since the factory likes to use the 6% slip figure, which is the right slip factor for rain/snow on street style tires. The only reason I want to go for 15% which is about the right figure for best dry traction, but the added wheel slip will compound with lateral slip to give me more "tail out" behavior. The small amount of front bias used to be drive neutral will also improve behavior on ice, hard pack, and in hydroplaning conditions over the normal viscous coupling or anything with a higher front bias. The cool thing is you can bypass the system for burnouts and dyno testing without any fear of damage with just the flip of a switch.

[ace_xp2]

Apparently the 246 had a 27 spline input when behind the 4l60, at least, the parts breakdowns say so:
http://www.tbtrans.com/transfer_case.htm
Also, can't seem to find it now, but I believe that someone out there found that the 136 and 236 case were actually the same, no saved space with the lack of low range. Haven't seen the 146, but it may be the same situation. Thus using the two speed case (second speed removed, unless you like crawling ) May not be the space/weight disadvantage that you may or may not have been thinking of...

[exwestracer]

I don't know what project you have in mind w/ a straight front axle, but I'd be more than happy to help research/find the right parts for it.

Nothing in particular. I'm used to stright axles on the supermodifieds, and it would be kind of an engineering exercise. There are ways to get camber gain and zero bump steer as well as dividing bump force from roll, but that's another discussion...

I'm thinking a "non-quick" Winters axle with aluminum tubes and build-up Wide 5 spindles. Still all unsprung, but it should be possible to get the whole works under 100 lb with brakes and rack.

Anyway, sorry to interrupt.

[Kenny]

Apparently the 246 had a 27 spline input when behind the 4l60, at least, the parts breakdowns say so:
http://www.tbtrans.com/transfer_case.htm
Also, can't seem to find it now, but I believe that someone out there found that the 136 and 236 case were actually the same, no saved space with the lack of low range. Haven't seen the 146, but it may be the same situation. Thus using the two speed case (second speed removed, unless you like crawling ) May not be the space/weight disadvantage that you may or may not have been thinking of...

You are correct. The 136, 236, and 246 are the same case. The main differences are the one piece input without the high/low range planetary, clutch disc count. and chain drive width. The oil pumps, seals, clutch basket, etc are interchangeable. The same goes for the 149/249 viscous type. The two speed planetary and parts account for about 12 lbs of added weight over the single range input shaft.

It is no surprise that you haven't seen the super rare 146, because I made it up. It would be, as you suspected, a 136 with the beefier 246 guts or a 246 with a 136 input shaft. I know that sounds like the same difference. The 2007 up 246 has the newer(better?) design servo motor and a close tolerance clutch basket to reduce clutch rattle. One thing I do wonder is if there would be any friction benefit to a roller style chain. I'm sure it would be an expensive proposition. I do like the full size case just because there is a lot of room left over to make a billet basket that would hold more clutches.

Nothing in particular. I'm used to stright axles on the supermodifieds, and it would be kind of an engineering exercise. There are ways to get camber gain and zero bump steer as well as dividing bump force from roll, but that's another discussion...

I'm thinking a "non-quick" Winters axle with aluminum tubes and build-up Wide 5 spindles. Still all unsprung, but it should be possible to get the whole works under 100 lb with brakes and rack.

Anyway, sorry to interrupt.

No interruption here bro! I see why you might wanna get away from electronics now. I really think a perfect TC for that application would be the 147 or 247 Jeep setup that uses a gerodisc clutch. There are guys using the front of a 249 and the rear of the 247(and the guts) to make a hybrid TC. Evidently the gerodisc clutch is FAR superior to the viscous coupling. I guess they are using the 249 front half to retain the factory flanges for their particular application. That system is RWD with automatic front apply as the rear wheels slip.

For the guys that don't know, the first number is the number of speeds or ranges, the second designates power capacity, and the third designates the type of clutch or drive.

[ace_xp2]

The 146 actually does exist, it's in the cherokee srt8. Since it's not common it's not cheap, so I thought you were looking to the 136 case from a size perspective. I didn't realise both the x36 and x46 series shared the same case though, good to know.

[Kenny]

DOH!! You're right! I just saw one on the interwebs! Sorry I doubted you. Now I gotta make up a new fake TC model #.... Another day shot to hell....and I was going job hunting darn it.

Check it out, I just got off the phone with another transfer case guru and he told me the Astro tcm is a complete standalone unit. All of these parameters can be controlled with simple resistor circuits too including continuously variable and on/off. He said the trick to the bias is as simple as clutch preload just like we thought. When I expressed the concerns the scooby guys have about it not being a proper AWD system his answer was " Those guys have been successful, but they have not gotten it completely dialed. This is a far superior system" That is another nudge in the forward direction.

Now to pin down more details. I wonder if the 3/4" chain drive from the 126 has substantially less friction than the 1.25" from the 246, and I wonder if cryo treating would help the strength difference. Cryo treatment seems to have made a pretty big difference on my old ATV and motorcylce race builds.....

[ace_xp2]

Just a tidbit here, I've noticed that some car based systems like this (aventador) get away with a smaller front diff than rear. It occurs to me that in 4x4 style vehicles, there may be situations where most of the torque is feeding through the front tires. Whereas, in a cars case, the only time that situation is likely to happen is when traction is low at all tires (snow/rain).
Anyways, there may be weight savings available in comparatively smaller shafts/diffs/etc. that will prove to be sufficiently durable in this application. Since front weight is rarely good weight it's even in a place where you'd want to lose it.
http://blogs.insideline.com/straight...alkaround.html

[Kenny]

Yes. The GM 7.2 IFS is fairly lightweight. The entire system is right at 140 lbs with transfer case, driveshaft, axles etc. Weight will be removed with aftermarket a-arms, C-6 uprights, and transverse composite leaf. Since the L-92 is all aluminum, the AWD system is virtually weightless compared to an iron engine car without AWD. The V-8 weighs less than the current V-6. I am happy that the weight is at least low in the chassis and not outside the wheelbase. I'm not sure that 2 diffs with more centered pinions would eat up any more power than a 9" Ford with all the pinion offset.

One thing that is readily apparent is that well tuned AWD works. I have been watching a lot of 2012 GTR vs whatever and it gives every supercar fits. You can watch it against the ZR-1 Vette on the racetrack and depending on the test they swap wins. This is important since the GTR has 100 less HP, 150 less torque, 500 lbs heavier, and less tire. It should not even be a race yet it is. Another thing to note is that most everyone says the other cars have a better overall suspension designs and the GTR beats them (including other AWD cars) because the GTR AWD is better tuned. The GTR suspension on it's own is not a world beater

I won't proclaim the GTR superior to the ZR-1, but I am more than confident the AWD system we are talking about would make the Vette faster around the track even with the 140lb weight penalty. On long stretches and top-end jaunts? No

[olason]

With the all wheel drive system, I was wondering if varying power put to the front by say a hydraulic pressure clutch or how do newer designs work. I guess my trailblazer ss is torque-sensing, but I don't like how it is built in with all the sensors in the vehicle. It could be much approved upon. Also with the T56 and adapter to the syclone transfer case, would there be a way to shorten the output shaft of the T56 and more build the housing of the T56 and transfer case together?

Any ideas how to make awd lighter and faster to modify into our type of cars?

[Kenny]

You have some good questions that I don't have really good answers for. You should have the T-3 Torsen unit in that dude since it is a SS. I think the T-3 is self actuating like a viscous unit, and all the sensors are for Stabilitrac to apply braking to the spinning wheel so the biasing center diff doesn't go fully "open". This is also AWD instead of RWD w/front assist. So if you were to remove the front driveshaft there is the potential for damage. The Silverado SS uses the 149 viscous coupling TC and there is no way to control how it behaves outside the factory calibration. The same goes for the BW TC in the Sy/Ty. There are guys using a billet 6 pinion planetary, which indicates the stock 5 pinion planetary has had problems in extreme conditions. The real problem in our road race application is more about the high amount of front bias these things apply and the loss of the front driveshaft will cause other problems.

There is one fully automatic hydraulic locking unit that could possibly be manipulated by restricting the oil flow into the gerotor pump after it leaves the primary pump. It is the Jeep 147 (single speed) or 247 (high/low range). I don't know how we get this to work in a GM application yet. We may be able to use the 149 front half with the 147 back half that contains the gerotor pump/clutch assembly. The input shaft would have to be addressed. This is also a RWD unit that applies front power as needed, but there is no way to unlock it for burnouts and dyno tuning without pulling the front driveshaft. That is the beauty of the Astro brain, we can bypass it with the flip of a switch. The only 2 sensors it uses are for front/rear drive RPM. I think the electronics are only really a hindrance when there are rules prohibiting it. Putting it all behind a T-56 is a question I have no answers for.

Now for the weight savings question......... I have considered using a tooth belt with hard coated aluminum gears instead of the all steel chain/gear setup, but durability fears persist and if the cost/weight savings would even be worthwhile. We could probably lighten the ring gear, scallop the diff flange, use carbon fiber driveshaft and axles. Again cost/benefit questions apply. There has also been consideration given to face tooth wheel engagement at the wheel hub (like detriot locker engagement) that could disengage the wheels from the drive axles for low drag on top speed jaunts and fuel economy considerations. Maybe use some electronic locking hubs..... again at a cost/weight penalty.

On the up side, there are a few suspension gurus working with me on this and they assure me that the performance benefits far outweigh the weight penalty, and if the ability to unlock the hubs at speed were implemented the would be no top speed penalty since aerodynamics are far more important than 140 lbs.

[olason]

You have way more knowledge into this than I do, but I am up and coming to the automotive world as I am only 20 and in college as a mechanical engineering student. I know RSGear builds an adapter that allows the sy/ty unit behind a T56 with use of the corvette transaxle "housing" instead of the tail-shaft.

My main concern is also packaging, I don't think it should hang too low, but I also am wondering how high it will extend into the passenger compartment. I know the sy/ty case is built out of aluminum, but it still looks "big" to me as it was designed to be used for many, many miles.

[calforniacuda]

The center diff in the trailbazer is a torsen, it it preloaded with 10% power to front. The torsen is some magical mechanical system that transfers instantaneously front and back, not using clutches or chains, only gears. The torsen is attached to a 4l65e in the trailblazer. I have a nv 247 with the the the low gears taken out, custom built and never used. let it go for cheap if you want.

[calforniacuda]

Using the trailblazer oil pan with the front diff bolted to it allows the entire tcase/front diff/axles to fit in the vertical engine bay clearance of most cars, just like the ss camaro awd. For your project why not use any number of somewhat sporty vehicles with a massively lower center of gravity. Without the trailblazer set up you are forced to go with a vehicle that sits high has a lot of vertical distance from the hood to the ground like the blazer to fit everything. just my 2 cents

[Kenny]

You have way more knowledge into this than I do, but I am up and coming to the automotive world as I am only 20 and in college as a mechanical engineering student. I know RSGear builds an adapter that allows the sy/ty unit behind a T56 with use of the corvette transaxle "housing" instead of the tail-shaft.

My main concern is also packaging, I don't think it should hang too low, but I also am wondering how high it will extend into the passenger compartment. I know the sy/ty case is built out of aluminum, but it still looks "big" to me as it was designed to be used for many, many miles.

If the SY/TY BW unit bolts up, the 136 would as well. From what I have seen, the BW unit is physically larger than the NV tc. The weight is similar, and both cases are magnesium

The center diff in the trailbazer is a torsen, it it preloaded with 10% power to front. The torsen is some magical mechanical system that transfers instantaneously front and back, not using clutches or chains, only gears. The torsen is attached to a 4l65e in the trailblazer. I have a nv 247 with the the the low gears taken out, custom built and never used. let it go for cheap if you want.

What does your "147" fit? It is a cool setup and should work very well.....
On the subject of the TBSS tc, it does still use a chain to drive the front driveshaft.

Using the trailblazer oil pan with the front diff bolted to it allows the entire tcase/front diff/axles to fit in the vertical engine bay clearance of most cars, just like the ss camaro awd. For your project why not use any number of somewhat sporty vehicles with a massively lower center of gravity. Without the trailblazer set up you are forced to go with a vehicle that sits high has a lot of vertical distance from the hood to the ground like the blazer to fit everything. just my 2 cents

I haven't seen much advantage in overall package height over a modded H3 pan. The key is whether you are using a different engine setback than a stock TBSS. The use of the TBSS pan does require some special consideration to get the axle shaft properly lubed to avoid bearing/axle spline failures.

To reiterate the reasons I have chosen this particular tc design (nv126/136/146):
1)eliminate the chronic understeer that too much power apply (front bias) causes
2)the ability to allow the rear tires to "over-run" the front by a percentage to allow me to tighten a line with the throttle (like a RWD)
3)the ability to manually turn it off for dyno testing and burnouts(tricks?)
4)it uses a standalone controller
5)my transfer case guys tell me it is the only design that is durable enough for the abuse it will see.

For those that have different priorities, I'm sure other designs can be made to work just fine.

[ace_xp2]

Ran across a few transfer cases which have an electromagnetic clutch setup. BW has them in models 4405, 4411, and 4416. The 05 and 11 are from the explorer, while the 16 is from the expedition. They may have even more models, I just happened to run across those.

[assquatch20]

Digging this up to say I'm very interested in tuning the TC. I'm looking to mate a T56 to a 4472 and stay mechanical, but a tuneable case sounds pretty awesome. I know I'd need to fab an adapter for a 4472. What about others? I'm assuming there's no OEM fit.