Is AWD mechanical socialism?

[Kenny]

Okay guys, I have been struggling with how to make AWD a viable performance/road race setup. After a long discussion with Mark Ortiz about my approach there may be some clarity. The project is a "03 Blazer.

The down sides of AWD are well documented. Sharing too much front wheel power with lateral forces cause push. Using a viscous coupling is not adjustable to drop the power percentage to the front and is not variable. Of course there is the added complexity, weight/distribution, and frictional losses. The advantages we are looking to exploit are forward bite, tail out driving without total loss of control and swapping ends, and improved brake balance (I'll explain later).

Here is the plan. Either a nv136 transfer case from a 99 up Astro/Safari with chain drive and clutches from a 246 tc or a 246 tc with the high/low range planetary removed and using a 136 input shaft. This gives a RWD drivetrain with front assist. As it comes from GM the control module allows very little wheel slip before the clutches apply to bring the front axle into play. The hard part is finding a way to adjust the computer to allow a higher percentage of slip. I'll be shooting for 10-15%. All of this can be juggled with clutch preload and programming.

One advantage of AWD is the ability to make the front wheels normally acceleration neutral by applying a small amount of front drive to keep them up to speed without being road driven, which would have the same effect as being required to pull too much. What I am saying is that on most of my vehicles, the front wheels are rolling at the same time the back wheels are while traveling down the road. Crazy! When braking there would be the advantage of stopping wheel lock-up with the tc helping keep the low traction wheel up to road speed........ Thoughts? Mechanical socialism with all that power sharing and such?

[jbake]

Well as with socialism its sounds workable on paper, but real life is not paper. Couple other problems I see is one, the front drive axles for your blazer would be IFS. Ask any off road rock crawler or mudder, these front ends are junk. They are even smaller than the 10 bolt in the rear. The cv joints are tiny as with axles. I had a 95 blazer with a 4.3 and 5 speed. I could not keep cv joints in pass side axle. Would blow about ever 500 miles and thats with factory 4.3.
Tire size also is a problem. You would need to run same size on all 4 or you will blow the TC apart. And it is not just same diameter but also same width. TC are pain in the rear. That's why I gave up 4wd n got into cheaper playtoys.
Good luck you are starting down a path the high blood pressure and balding. Eather stress will make you bald or you ripping your hair out.

[Kenny]

It seems that when something works on paper, but not in real life, there has been some pertinent information left out of the paperwork. I have been dealing with S-10s for about 20 yrs just because they are my favorite platform. I have seen 2 front diff failures out of dealing with dozens of trucks and they were due to neglect or abuse. both failures were on the same truck with 200k + drivetrain miles. It was, as you mentioned, a rock crawler guy with a V-8 and 30+" tires. He smoothed off a pinion gear and later lost the spider gears. Once he let us know the front diff would unlock under full throttle(low vacuum), and suddenly engage again with one tire off the ground, we replaced the diaphragm with a manual locking mechanism and the problem went away. I will not have the axle that is engaged part time. I have never seen the chronic CV failures that you experienced even when dealing with some real hotrod Sy/Ty clones using the aluminum case.

The tire height issue is not a problem with my tire selection, but the fact that this will be modified to allow more wheel slip % will reduce or eliminate that issue. There is also the possibility of adjusting the computer to read a front and rear speed with pulse differences as normal (not sure if that made any sense). So many of the objections in my mind have been overcome. The remaining objections that I had involved the open front diff. That is in the process...... I am working with the possibility of having a waveloc diff custom built off an existing core. This will give gear style differentiation without going completely "open" like the Truetrac or Torsen. Another fear is the smoothness of engagement. Working with careful tolerances, basket surface prep and treatments, and preload settings are things that will receive careful attention.

The main concern of this posting was how to get the dynamic handling behaviors we all like, and it looks like 10-15% wheel slip will give predictable tail out driving goodness.

[exwestracer]

I can't speak to the technical end of it, but I'm amazed at the AWD system in our new 2011 Charger. It's the earlier gen M-Benz 4matic system, and engages the front drive based on various circumstances. I've had that car in a 4 wheel drift, felt the front drive kick in, and it just tucks the nose back toward the inside of the corner. I know it apparently violates the laws of physics, but I've done it; and I'm sold on "smart" AWD as Dodge does it.

[Kenny]

That is exactly what I am looking for....... Evidently the weight/ drag issues don't even come close to negating the advantages when it is even close to right. This is considering that, in the mountains, we don't have a lot of open straight stretches where it might lose it's advantage. Even with that being said, we always have weather, dirt and debris on the road, etc..... I just don't see a down side for my personal daily driver. The settings of the GTR system is where I will baseline since it is just so good


http://www.youtube.com/watch?v=CNAI0e3oqU0&feature=related

http://www.youtube.com/watch?v=PtrUSa7DexU&feature=related

[nine lives johnny]

52048
well awd platforms can be used in a performance/road race application. we've built and raced/built with an sti, evo, and audi tt. can an 03 blazer be any good? well i wouldn't put the qestion to if your stock parts will hold up, but will your car be safe? generally in auto x road racing you dont need to beef up your drive train componets as much as you would when building a drag car. the blazers center of gravity is very high even when lowered (on awd platforms). i would be more worried about the thing rolling over. any precautions to stop it from rolling over, would make it lose allot of road manners and be uselless of road. blazers have a towing copacity of 6k lbs. i would take money that you where going to invest in the blazer and buy a 1980's f body or fox body. it will cost the same, and use the blazer to tow it to events. or get a 2wd truck to race. my .02

[Skip Fix]

Might look at the old Typhoon/Syclone GMC trucks that were basically a Buick GN with AWD in a truck./SUV platform. Some of them were pretty bad a$$ and dropped pretty low.

[Kenny]

52048 well awd platforms can be used in a performance/road race application. we've built and raced/built with an sti, evo, and audi tt. can an 03 blazer be any good? well i wouldn't put the qestion to if your stock parts will hold up, but will your car be safe? generally in auto x road racing you dont need to beef up your drive train componets as much as you would when building a drag car. the blazers center of gravity is very high even when lowered (on awd platforms). i would be more worried about the thing rolling over. any precautions to stop it from rolling over, would make it lose allot of road manners and be uselless of road. blazers have a towing copacity of 6k lbs. i would take money that you where going to invest in the blazer and buy a 1980's f body or fox body. it will cost the same, and use the blazer to tow it to events. or get a 2wd truck to race. my .02 Nice...... tip over much do ya? This is an exercise in handling and will never see off road (intentionally). While the the truck will be a bit lower and many low mounted components. The CG may not be that out of line, and if we were to check closely, it may have a better CG height to track width ratio than what you have worked with. I'm guessing that getting the roll center correct for balance is gonna be most important followed closely by really good shock valving. I like that you chimed in because the topic always brings about the dominance factor of AWD in the cars you just mentioned, even though in theory they are the worst platforms you could start with being front drive with rear assist (too much front power to be ideal) and associated balance issues. Maybe you could give me some insight as to drive and wheelslip percentages that you used to stop push or even do some tail out dirt track style driving. Just in case the point hasn't come across, wheel slip percentage manipulation will be used for four wheel drifts rather than just wagging the rear out with weight.

[nine lives johnny]

kenny,
i must admit that i'm not the guy that sets up the diffs on the awd cars, and as far as distribution percentages down i don't know what's the perfict % is. generally we try to get as much power to the rear as we can. audi tt's are built with 75% of the power headed to the front tires. that's why we leave that chassi behind. it's too hard to get it to stop under-steering (pushing) when you get on the power. first things first when your looking into setting up your chassis forget about power and where it goes. you have a blazer, i assume your cross weight is 60-70% over your front tires. this means your blazer will generally push threw turns without any power being added. your fount tires are being put to the limit, now add in the fact that power is going to go to those wheels, and kiss going around a tun good buy. i know you want to have your car act similar to a gt-r but it won't. i think if you invest 20grand into your car it will handle similar to an wrx (not a wrx sti). expect lots and lots of understeer. seriously the blazer is a good tow rig, pick up a sti or some other sports car. you'll be much more happy.


if your dead set on a suv racer (and it sounds like you are) look into this http://www.jeepsunlimited.com/forums/showthread.php?t=531598

[Kenny]

I'm not sure what the cross is but it scaled out at 3860 with some fuel. It was right at 2000 lbs up front and 1860 rear which figures around 52%/48%. No lightening has been done yet. The L92 weighs about 30-35 lbs less than the V-6, the battery will be 35 to the rear (effectively 70), and my torque converter is supposed to be 20 or so lbs lighter than stock. It will get near 50/50 but I wouldn't sweat it at 52% front. I have already gotten rid of most push with the 245/60-15's I have now by doing nothing more than using ZR2 torsion bars cranked all the way down, alignment work, and fresh Bilsteins. This setup will give way to a junkyard transverse leaf from a '06 vette, which should be a little stiffer if I need it and knocks off a couple more lbs........ I'm giving it the ol' hillbilly try.

[Kenny]

kenny, this means your blazer will generally push threw turns without any power being added. your fount tires are being put to the limit, now add in the fact that power is going to go to those wheels, and kiss going around a tun good buy. This is a very important part of the conversation that only got glossed over in the first post. Power is always applied to drive the front wheels even in a RWD only vehicle. The front tires in a RWD are road driven rather than axle driven, but they are still receiving forces other than lateral to keep them up to speed. This has the same effect as applying a little too much power. Part of the "system tuning" is applying a very small amount of drive to make them "drive neutral". I know this seems insignificant, but I have been assured that there is substantial benefit in lateral traction and predictability. The Nissan system is defaulted to a 98/2 split. It seems that the 2% front assist has a measurable effect and is beneficial for reducing "push". This can also have deceleration implications as well. Think of a lightly loaded inside wheel that locks up, using (sharing) the same energy through the AWD system. This will keep the wheel up to road speed that would normally lock, while transferring the braking power from that rotor, that would normally be wasted, to the other wheels.

[nine lives johnny]

well the cross weight is not to bad. what is your power distribution for your center diff? your planning on doing a l92 swap too? you gotta hack the crap out of the oil pan to fit one into a awd platform. be well aware of the oil starvation with lsx type blocks, get your self an accusump before you hit the track. sounds like your ol' hillybilly try is going to some uncharted watter. keep records and do a build thread. i would love to see something different.

[Poopy]

Instead of messing around with GM truck stuff, why not get your hands on a wrecked Subaru and build a new frame with a proper AWD system??

[Kenny]

Instead of messing around with GM truck stuff, why not get your hands on a wrecked Subaru and build a new frame with a proper AWD system?? With the discussions I've been having with some serious suspension engineers, and the way it is being implemented, it appears that GM truck stuff is likely a more "proper" system than the scooby doo stuff. Even though the Subaru stuff has been made to work well, it is almost the exact opposite of proper. The best part is I'll be able to toss a few bags of pavement patch, some Quikrete, and my freon tanks and gauges up in that pig and make some money........


well the cross weight is not to bad. what is your power distribution for your center diff? your planning on doing a l92 swap too? you gotta hack the crap out of the oil pan to fit one into a awd platform. be well aware of the oil starvation with lsx type blocks, get your self an accusump before you hit the track. sounds like your ol' hillybilly try is going to some uncharted watter. keep records and do a build thread. i would love to see something different.Man you gotta ease up on the negative vibes...... The H3 pan fits with no mods if you space the front diff 3/8-1/2" or you can do a mild scallop. For power split we are looking to get down to a 98/2-95/5 split. It will start with about 50lbs of clutch preload (stock is 200lbs). There is still a lot of information gathering and math going on......

There will be those warning of CV joint problems with diff spacing and a spindle drop but they just aren't that sensitive to mild changes. If they were, the factory wouldn't put them on the wheels you steer with. The problems come in when a kid rolls in with a 200K mi Honda that has established a very distinct wear pattern and they drop the thing 3"

[Kenny]

Sorry, double post

[exwestracer]

This is a very important part of the conversation that only got glossed over in the first post. Power is always applied to drive the front wheels even in a RWD only vehicle. The front tires in a RWD are road driven rather than axle driven, but they are still receiving forces other than lateral to keep them up to speed. This has the same effect as applying a little too much power. Part of the "system tuning" is applying a very small amount of drive to make them "drive neutral". I know this seems insignificant, but I have been assured that there is substantial benefit in lateral traction and predictability.

THAT is a VERY interesting concept, and perfectly explains my experience with the Charger. Thanks.

[nine lives johnny]

Man you gotta ease up on the negative vibes......


sorry man.. The inner racing purest in me is screaming you can't race a blazer, but the artist in me is saying why not.
I mean this seriously and with out sarcasm.
go for it! shut up my inner racing purest.
good luck hope to see you at LS Fest. I'll have the miata. :thumbsup:

[Kenny]

THAT is a VERY interesting concept, and perfectly explains my experience with the Charger. Thanks. You handled that just like I did when the theory was presented. It was like turning a light on.


sorry man.. The inner racing purest in me is screaming you can't race a blazer, but the artist in me is saying why not.
I mean this seriously and with out sarcasm.
go for it! shut up my inner racing purest.
good luck hope to see you at LS Fest. I'll have the miata. :thumbsup: I know what you are saying, and I must admit that naysayers are the fuel for my fire. The objection of others always brings about considerations that MUST be overcome to make a successful project, so I really need the negative vibes.... I am going more for the definition of "pro-touring" that fits my needs than a racer. The roads in my neck of the woods are really bad for a race RWD set-up compared to AWD when there is serious power. The tight turns, stutter bumps, and banked switchbacks are horrible for traction, nevermind the occasional bump that will almost pitch the rear off the ground. A true road race RWD would not fare well against AWD.
Just like the old saying, I know I can't turn that pig into a racecar, but I can make a damn fast pig! I'll go WEEE,WEEE,WEEE all the way home :6gears:

[exwestracer]

You handled that just like I did when the theory was presented. It was like turning a light on.



While I definitely will NOT be tweaking the AWD system in the new Charger, your point did bring up a whole new line of thinking regarding instantaneous variations in F/R torque split. This kind of goes along with another idea I've had kicking around for awhile: using hyd. displacement directly from suspension travel to mechanically adjust torque split.

Hmmm, I wonder how light I could make a solid front drive axle.....

[Kenny]

On a side note I have been looking at your 2011 system and it was changed on '09-up to on demand like the system we are talking about for the Blazer. Nice.

The hydraulic method you mention was looked into as well as weight jacking for the low traction wheel, then I ate lunch and forgot what I was thinkin'.....

One of the things that is most interesting is the control boxes are often programmed to "anticipate" need by comparing yaw, acceleration rate, throttle position etc. If you are going at a low road speed and it senses a rapid rate of throttle opening by the TPS and it will just assume you are gonna have a traction problem and deal with it accordingly. That is my favorite part of EFI, it is actually pro-active instead of reactive like a carb.

Aside from the "neutral front wheels", the prospect of using this to control braking is very exciting as well. The prospect of taking out rear bias because of inside wheel lock-up always seemed like a waste because it only helps in that instance, meanwhile you are just giving up braking power in every other situation, and ABS is just too heavy handed.

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.

[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/straightline/2011/09/2012-lamborghini-aventador-suspension-walkaround.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.