ebrake question

i know there was another thread before on this same topic, however i was unable to find it. so i will start at new one.

in the last thread we were discussing the pros and cons of using the ebrake(for fun) on a AWD vehichle. i am not sure what was concluded in that thread, so i am opening discussion again.

some points to touch on:

differentials
prolonged use
short stabs
long term/expensive damages?

Thanks

 

replying on behalf of the manual tranny subarus.

differentials
The 5spd manual center diff acts/works just like ever other diff. The special thing that it has is a viscous coupler, which will try to keep the "ends" from spinning at a different speed from either other. These ends are the outputs to the front and rear wheels. ALL open diffs send equal power 50:50 to either wheels, that is until one wheels starts to slip and because an open diff doesn't have LSD function, that slipping wheel will get more power to it.

In a sense, what they call "transferring torque" from left to right, or front to back isn't really what it is. Lets look at a simple VLSD that's found in the rear of the '00-'01 RS and WRXs. When BOTH rear wheels are on the ground maintaining 100% traction, BOTH of them are putting out 50:50 of power left to right. Now when the right wheels slips, this power will be more like 25:75 left:right. IN certain situations, it'll even be 5:95 left:right because the VLSD isn't the BEST LSD out there. Basically the viscous coupler is trying to resist speed difference, but it is not transferring power anywhere, just trying to hold the torque from the wheel that's gripping to the wheel that's slipping. This is the same with the center viscous coupler as with all viscous couplers.

If you know how it works mechanically, really it's very simple.

Now when you pull the e-brake and lock the rear wheels it'll try to slow the front wheels down as well because the rear's arn't spinning anymore.

prolonged use / short stabs
Depending how long you do this and how fast you're gonig will determine the wear rate upon an insufficient working center diff (thus where you can then take it out, weld it, and make the car run RWD). Quick stabs are fine especially on snow because if you noticed, it DOES LOCK the front wheels due to the slippery surface. I've seen it. And when I was doing my donuts on dry pavement, I was at low speed and just a quick stab, that's it. It's no different than getting stuck and spinnin the front wheels or rear wheels.

long term/expensive damages?
The center diff isn't hard to take out, remove the rear cover after removing the linkage joints and driveshaft then pull it out with the transfer gear assembly. What'll cost would be the center diff.

The auto is clutch type stuff, OR like the WRX and Outback which uses planetary gear-style center diff with LSD effect (very similar to the STi/STI's DCCD system)[/b]

 

i know the STis (atleast the 6spd DCCD ones) have an eletric switch that disengages the center diff when teh ebrake is pulled. in the above statement are you saying that the 4eat trannies have the same ability to disengage the center diff?

also referring to lockign the front wheels, the ebrake on imprezas (not true w/ all subaru (GLs/Loayles are different for sure)) while effect the back wheels. are saying that when the e brake is pulled and the back wheels are locked that the center diff will also lock up the front wheels? from my expeirences on snw this was not true. can i get some more clarification on this part?

 

I have a question too, it will mostl likely sound dumb to all of you but I can not figure it out.

What does LSD stand for?

 

Limited Slip Diffrential.

 

Thanks Shane86

 

OK so i might use my ebrake too much, how would i go about tightening it?

 

if you take off the center counsel you should be able to adjust the ebrake cable. i think its just a bolt or two that hold the cable to the lever, and you would just need to lossen the bolts and re tighten the cable. i have not done it before, but thats how it should work.

 

There are actually two methods to adjust this.
if it's just starting to get loose, you can do the under console thing. but after looking at it on my own car, it doesn't look long enough to do any serious adjustments. like 5+ clicks.

The other one is in the parking brake asemblys on the rear wheels themselves.
they can be adjusted with a screwdriver from under the car without taking the wheels off, but they're supposed to be in the air so that you can tell by turning them how tight the brake is.

See this link for all the info:
http://www.scoobymods.com/forums/showthread.php?t=2779&highlight=adjust+Brake

 

4EAT doesn't have a switch (as far as I know) and that the clutch type LSD will simply wear a slipping disc as the ebrake is used while in motion.

On the WRX, the VLSD has quite a bit of mechanical resistance. This is one of the reasons you slow down while turning. As far as on the snow and ice, the front wheels will only lock if the mechanical resistance through center diff is greater than the static forces (traction) of the front tires. You would need crappy front tires for this to occur. If you are going fast enough, and have good traction front tires, clutch and pull the ebrake in a quite environment and you will hear the VLSD working its heart out to keep the engine from stalling. It is the sound of the planetary gears going round really fast.

Fuji, is this info correct?

~Dan

 

as far as adjusting the ebrake,
I had my rear brake adjusted on the caliper, not on the console, thats probably the way you should go, not the console route, 5 minute job for someone who knows what they are doing.

 

The sound would be the spiders gear running around when the speed front to back is different in the center diff. It's a wining noise that gets transmit out.

 

this makes sense. the older 4eats (not sure about the new ones) have a spot to put a fuse in the engine bay to disengage the center diff and allow the car to run in FWD for towing / limping purposes. it makes sense that if you connected a relay to the fuse. you could pull the brake (engage relay) and become FWD and thus no harm to center diff.

hmmmm........

 

so the STi doesnt use a vlsd in the rear?

 

STi has mechanical rear diff. I think it's a Suretrac. People say if you lift a wheel it doesn't work, but then that would suck because it's a LSD, why would that happen......apply brakes and it'll transmit torque to lock up the diff and the nit'll work they say. *sigh*