Manual VS Auto for AWD

[Setright]

HOW MANY FLUIDS GET MORE DENSE WHEN THEY HEAT UP?

 

 

The VC fluid expands as it heats up and presses the plates closer together. The drag in the oil prodives the drive.

[NorthWet]

The 92 FSM shows a torque-multiplication curve, and max multiplication is around 2.4 at 0 output rpm.

 

Viscous coupler fluid becomes more viscous as it is subjected to shear forces. Couldn't remember the term, but Wikipedia says that the fluid is dilatant. (Cornstarch can be mixed with water to create a dilatant.) It has little to do with temperature or pressure, but rather shear forces on the molecules.

[fnlyfnd]

50/50 split means that if one wheel slips then the others will essentially stand still: Small amount of torque (maybe 1-5ft-lbs) to keep the wheel slipping and THE SAME FORCE to the other wheels. All of the rest of the "power" doesn't exist; an engine in neutral at 4000rpm isn't transmitting any power, and an engine spinning a wheel with an open diff isn't developing any more power than to spin the wheel.

 

What . The 50/50 is front to back when people are refering to manual awd. So I don't really understand your statement. I have had all 4 spinning on ice, and front and back spin. so how do you say that if one slips then the rest stand still?

 

And for the question at hand. I would rather have a auto for offroading, but love my 5spd that has gotten me thru some pretty muddy stuff, and the snow is a lot of fun.

[nipper]

HOW MANY FLUIDS GET MORE DENSE WHEN THEY HEAT UP?

 

 

The VC fluid expands as it heats up and presses the plates closer together. The drag in the oil prodives the drive.

 

http://www.cars.com/carsapp/boston/?srv=parser&act=display&tf=/features/mvp/vpedia/viscous_clutch_popup.tmpl

 

A limited-slip device that uses heat-activated viscous fluid to transfer power between two driveshafts

 

Serving the same duty as a limited-slip differential, viscous couplings are most often used in all-wheel-drive systems in place of a conventional center differential: The viscous coupling connects the front and rear driveshafts and allows them to rotate at slightly different speeds during turns. But when the rotational difference between the axles increases, as when the pair of primary drive wheels slip, the viscous coupling then binds the axles together and transfers power to the opposite axle and wheels.

 

“Viscous” refers to the fluid encased in the device, a silicone gel so sensitive to heat that it thickens and expands in fractions of a second. Metal discs on the opposing driveshafts rotate in this fluid, more or less at the same rate. When one set of discs spins significantly faster than the opposing set, it “shears,” or churns, the fluid. The resulting friction generates heat that causes the fluid to thicken and expand, which transfers the rotational force of one axle to the other, even though neither shaft is ever directly in contact with the other. The viscous fluid thickens and thins so quickly based on incremental temperature changes that a well-designed coupling can vary the amount of power it transfers to match the demand. Viscous couplings are simple but effective devices that require no sensors or computer control.

 

[nipper]

What . The 50/50 is front to back when people are refering to manual awd. So I don't really understand your statement. I have had all 4 spinning on ice, and front and back spin. so how do you say that if one slips then the rest stand still?

 

And for the question at hand. I would rather have a auto for offroading, but love my 5spd that has gotten me thru some pretty muddy stuff, and the snow is a lot of fun.

 

get one wheel of each axle on ice, and one wheel on solid grounds, then you will spin and not move. All 4 wheels on equally slippery surfaces will wpin, since the torque goes to the wheels with the least traction. on ice its all of them.

 

nipper

[Setright]

True Nipper, but you'd have to really stomp on the pedal to produce pure runaway wheelspin.

 

If you're sensitive with the clutch you could move off. The drag in the oil inside the side-to-side diff and friction in the drivetrain means the diffs aren't 100% open in practice.

[nipper]

hehe from reading this list all this time, i tend top beleive people stomp on the pedals a lot... i know i do for the hell of it on snow and ice

 

In a manual i would start in second gear on snow and ice to avoid wheel slip.

 

nipper

[98obster]

on newer generation Subaru's (EJ) the manual trans do not have the option to lock the center diff. BOO for SUBARU for not keeping that trait of the older generation models. for automatic trans subarus you can install a duty solenoid C switch and control lock up of the transfer clutches for the rear. this will essentially "lock" the front and back, the car will hop and jump like a truck in 4WD. can't do that with the manual trans, the center diff will always remain open.

 

on older model manual transmissions (EA, ER series vehicles) they offered locking center differentials and even dual range. those are great vehicles in terms of 4WD capability.

 

 

the "snow switch" (picture would be inserted if I could )is a great way to update our 4eat subarus. If you are starting out in deep snow and need to gain sure-footed speed. On the new Jeep Compass it is called "locking center coupling". It is strange that subaru's AWD-centered thinking has overlooked this option.

 

Oh, and I don't miss riding the clutch while crawling up I-70 at 5 mph in Colorado on Sunday afternoon with the rest of the world. Hill holder is wonderful. Auto Subies are great-most manufacturers don't have 1-2-3-D-N-R-P just D-N-R-P.

 

Good article on the 4x4 rage in car manufactures these days:

http://www.skipressworld.com/us/en/daily_news/2006/09/winter_wheels_do_skiers_really_need_4wd.html?cat=Snowlife

 

Jon

[cannonball]

the "snow switch" (picture would be inserted if I could )is a great way to update our 4eat subarus. If you are starting out in deep snow and need to gain sure-footed speed. On the new Jeep Compass it is called "locking center coupling". It is strange that subaru's AWD-centered thinking has overlooked this option.

 

Oh, and I don't miss riding the clutch while crawling up I-70 at 5 mph in Colorado on Sunday afternoon with the rest of the world. Hill holder is wonderful. Auto Subies are great-most manufacturers don't have 1-2-3-D-N-R-P just D-N-R-P.

 

Good article on the 4x4 rage in car manufactures these days:

http://www.skipressworld.com/us/en/daily_news/2006/09/winter_wheels_do_skiers_really_need_4wd.html?cat=Snowlife

 

Jon

 

IIRC some of the guys here have been able to add a switch to the solenoid switch that will lock the center diff. I also think that the split for the 4eat is 50/50 in 1 and 2 gear although not truely locked.

[idosubaru]

IIRC some of the guys here have been able to add a switch to the solenoid switch that will lock the center diff.

yep, for a couple years on two different vehicles. i've used it plenty, it's awesome. since the EJ's don't come with center diff lock options, this makes the auto equal to or better than the manual.

[Manarius]

IIRC some of the guys here have been able to add a switch to the solenoid switch that will lock the center diff. I also think that the split for the 4eat is 50/50 in 1 and 2 gear although not truely locked.

Yes. A guy on SL-I has implemented a switch of this sort. It makes the Solenoid go to duty 100% to make 50% split.

[Wayne Boncyk]

Yes. A guy on SL-I has implemented a switch of this sort. It makes the Solenoid go to duty 100% to make 50% split.

 

Manarius, I don't get it. With the 4eat, turning on the Duty C solenoid 100% locks up the system in Front Wheel mode. That's why you can switch to FWD mode when a fuse is inserted in the FWD socket; you turn the Duty C solenoid ON full time when that fuse is there.

 

It is only when the Duty C is OFF (or stuck) that the 50-50 front-rear coupling is constant. So, maybe what they really are doing is interrupting the control voltage to the Duty C solenoid with a switch that is opened when you want "full time" 50-50 split. I can see where that would work, but I can also see where that would throw AT codes and cause your AT Temp light to flash on startup -- not a good thing unless you know what's really going on there.

[Wayne Boncyk]

Or, is this a MT only thing and did I just confues myself? It's been known to happen! :-\

[BigMattyD]

I found two interesting websites, one explains the basic operation and has some photos of a typical viscous coupling. The other has technical information regarding the principles behind viscous coupling, which is the study on rheology.

 

The liquid in the VC is probably not water-based, but a similar principle applies. The VC liquid is a relatively thick fluid that can almost immediately thicken even more when a shear force is applied. This is the same principle listed on the second website known as dilatancy. And yes, the classic example is the cornstarch/water mixture that somebody else previously mentioned.

 

It is not due to heating of the fluid, but the actual physical force (sliding, or shear force) applied across a thin film of the fluid that allows it to thicken and "lock-up" the plates of the VC. Anyway, this information was new to me, and I thought it was interesting.

 

matt

 

http://www.answers.com/topic/viscous-coupling-unit

 

http://www.lsbu.ac.uk/water/hyrhe.html

[idosubaru]

correct on the Duty C solenoid. this has already been discussed at length in other threads. yes the POWER light (or other AT light) blinks on start up if the power is cut to Duty Solenoid C. if it's "off" (normally wired), which it almost always is, then no light blinking. i also have my shift resistor unplugged so mine blinks every time i start the car anyway. shifts much better that way and i can plug it in if i ever needed to troubleshoot, not that i've had to.

[Manarius]

Manarius, I don't get it. With the 4eat, turning on the Duty C solenoid 100% locks up the system in Front Wheel mode. That's why you can switch to FWD mode when a fuse is inserted in the FWD socket; you turn the Duty C solenoid ON full time when that fuse is there.

 

It is only when the Duty C is OFF (or stuck) that the 50-50 front-rear coupling is constant. So, maybe what they really are doing is interrupting the control voltage to the Duty C solenoid with a switch that is opened when you want "full time" 50-50 split. I can see where that would work, but I can also see where that would throw AT codes and cause your AT Temp light to flash on startup -- not a good thing unless you know what's really going on there.

Well, perhaps I swapped my cycles...I always forget which % cycle makes which %split. However, I know a guy on SL-I has made such a switch without problem.

 

losdiosdeverde86 is his name.

[BoostedBalls]

Ok, OK, but the real question here is: Where is the duty solenoid C? I got some serious bind in my 93 Legacy. I'll go as far as drop the valve body but deeper into the system is no man's land for me.

 

Besides, I realized a while back while watching my wife (she's from Asia and never drove a car until a couple years ago) back out of the driveway that she has been hitting the gas in drive before the transmission has time to 'grab'. This results in a nice jerking action and me standing there with an "oh crap I'm gunna be replacing that transmission soon" look on my face. She stopped doing it after I schooled her a bit but I got a call from her today stating that the engine revvs up while she's cruising at a constant speed. This thing has almost 200k on it and doesn't leak. I'll check the fluid level but I think it's time for a replacement anyway.

 

A lot of guys on the group complain that their wives don't know how to drive a stick, well, mine can't even drive an auto!

[seanski06]

 

A lot of guys on the group complain that their wives don't know how to drive a stick, well, mine can't even drive an auto!

\

 

 

haha thats good stuff

[idosubaru]

boostedballs,

the duty solenoid C and clutches are located in the rear extension housing, accessible without pulling the transmission. you can swap clutches and solenoid or swap an entire extension housing for your old one.

 

but...for the cost of those parts you can probably just find a good used trans to swap in.

 

might want to try a transmission fluid flush to start with. all the tires match?

 

so it's binding and it's reving up as well? more than one symptom? might want to start another thread for your problems....

[Dante]

on newer generation Subaru's (EJ) the manual trans do not have the option to lock the center diff.... for automatic trans subarus you can install a duty solenoid C switch and control lock up of the transfer clutches for the rear. this will essentially "lock" the front and back, the car will hop and jump like a truck in 4WD.

 

Good to know. Now I know my pre-96 EJ22 wagon will be an automatic. I had an old Datsun 510 with oversized tires and an automatic that I took some amazing places (e.g. up the "zorro road" above Granite Lakes past the saddle above Gifford Lakes). The slush box made it easy to ease the car forward without spinning the tires.

[Wayne Boncyk]

I agree with grossgary. Try a full fluid flush (at least 4 complete drain and fills, with just enough driving in between to flush all the old stuff out from the nooks & crannies if all you're doing when you empty it is pulling the drain bolt on the bottom of the tranny pan). After that, then try driving slowly through a few figure 8s in a parking lot. If the bind doesn't noticeably decrease, then pulling the rear extension housing on the tranny is your next step. He's also right in saying that if you end up replacing all the parts in that extension housing with new, then you're probably better off just swapping the tranny. However, if your problem is only a sticky Duty C solenoid then for under $100 in parts (new solenoid and extension housing gasket) plus some new tranny fluid you will solve your problem. Its actually one of the easier repairs to do on a sube powertrain. Hardest part is breaking free the 11 (I think its 11) bolts that hold the extension onto the back of the tranny housing.

 

And nipper will probably again complain (as he almost always does when I suggest this) but I'm a believer in synthetic AT fluid -- my 4eat runs MUCH smoother since I switched to synthetic.

[nipper]

Yes. A guy on SL-I has implemented a switch of this sort. It makes the Solenoid go to duty 100% to make 50% split.

100% duty makes the duty solenoid now an on/off solenoid. 100% on is 2 wd. 100% off is 50/50 split.

If you dont mind the tranny temp light yelling at oyu everytime you start the car then its fine.

But keep in mind the few times somone just throws a switch in, they come back a few months later saying their clutchpack is fried.

There is the fast and dirty install, and a proper install, which makes the TCU happy, and helps avoid forgetting that the switch is in the one position (using a drop out relay and a couple of push buttons).

 

nipper

[idosubaru]

But keep in mind the few times somone just throws a switch in, they come back a few months later saying their clutchpack is fried.

i've installed a simple 2 pole switch and it works great. i use it all the time, no transmission problems after a couple years of use. why would the switch cause the clutches to be fried? i haven't seen that problem and as far as i know, the other guys on the board here and at http://www.xt6.net installed it the same way.

[idosubaru]

But keep in mind the few times somone just throws a switch in, they come back a few months later saying their clutchpack is fried.

i've installed a simple 2 pole switch and it works great. i use it all the time, no transmission problems after a couple years of use. why would the switch cause the clutches to be fried (not including mis-use on pavement and what not!!! i haven't seen that problem and as far as i know, the other guys on the board here and at http://www.xt6.net installed it the same way.

[nipper]

I

 

And nipper will probably again complain (as he almost always does when I suggest this) but I'm a believer in synthetic AT fluid -- my 4eat runs MUCH smoother since I switched to synthetic.

 

 

nipper