5mt driveshaft question

free5ty1e · Post by **free5ty1e** » Wed Jun 02, 2004 1:00 pm

lol... not that I have trouble getting the Legacy sideways, just that I haven't had the opportunity to do so yet. Been learning about the particulars of the car since I bought it, making sure it's in good shape - havent even been to the drag strip yet to get a quarter time.

So... the 5MT's have some decent strength to them, this is good. We do have LSD's, not open, correct? My Saturn was open diff and man you had to be careful with one o'dems, one wrong throttle move and you become a one-wheel wonder. Not to mention they had a serious flaw in every year/model where one-wheel burnouts=diff pin spit out tranny case.

Any of you in Florida? We should go surprise some ricers.

THAWA · Post by **THAWA** » Wed Jun 02, 2004 4:30 pm

all usdm bc/bf legacies have open diff's except some 91 models. oh and the center in 5mts (that's a lsd right?)

BAC5.2 · Post by **BAC5.2** » Wed Jun 02, 2004 4:51 pm

Yes, the center is LSD in ALL 5-MT's. It's a Vicous Coupling unit. I'd prefer a torsen unit, but what are you gonna do?

Chris - Supposedly, the Turbo Legacy 5MT is one of the strongest trannies to hit the US shore. Still not that strong though.

Most FWD cars have the diff-pin problem.

free5ty1e · Post by **free5ty1e** » Wed Jun 02, 2004 6:13 pm

That's good to know... what about if your particular Legacy originated in Canada? Any difference there?

So if I'm understanding correctly, we have center LSD but perhaps open differential between the left/right on each axle? Or LSD on all four wheels? I'm new to AWD

(Yep, I've seen quite a few one-wheel wonders at the drag strip... most times they dont know what they're doing and you kinda feel like tellin them thats not good but then again...)

BAC5.2 · Post by **BAC5.2** » Wed Jun 02, 2004 7:42 pm

An LSD is a Limited Slip Differential. A diff is located everywhere power is split. At the center (which in our cars is an LSD), and one for the front end and one for the rear.

Unless you have a 1991 or 1992 Sport Sedan, you don't have an LSD from the factory. I am fairly certain that those are the only two years that the LSD was an option.

free5ty1e · Post by **free5ty1e** » Wed Jun 02, 2004 8:13 pm

Right... so we've got limited slip between the front and rear, but for my '94 I've got open differentials on the front and rear axles?

By the way... is the torsion LSD the same as used in the old muscle cars that had positraction? As in... its actually got a clutch in there that engages when one wheel is spinning a certain amount faster than the other?

If so, I'm guessing our viscous coupling LSD is kind of like an auto trans, where it uses the fluid itself to transfer power - so all we have to do is change the fluid as opposed to changing a diff clutch.

Am I correct? (at all? lol)

mikec · Post by **mikec** » Wed Jun 02, 2004 8:18 pm

I thought just MY91 came with a rear LSD. I know my 92 doesn't have one.

Brat4by4 · Post by **Brat4by4** » Wed Jun 02, 2004 8:23 pm

The rear LSD was standard in '91 and a rare option in '92 (and maybe other years).

Yes the fluid thickens from friction and subsequently sends more power to the side not spinning. The fluid itself is not serviceable (supposedly). Only the gear oil is changed in the tranny and rear end.

For an explanation of all the LSD types, do a google search. It is amazing what the internet can contain

. I would recommend searching for differentials rather than the term "LSD", though.

BAC5.2 · Post by **BAC5.2** » Wed Jun 02, 2004 11:55 pm

Chris - A TORSEN unit is a TORque-SENsing unit. Nothing like a posi. A posi uses clutches, like you said. A TORSEN unit uses a planetary style gear setup to limit slip.

free5ty1e · Post by **free5ty1e** » Wed Jun 02, 2004 11:59 pm

whoa... OK I thought that was just a typo. The torsen unit sounds like another friggin transmission! Thanks

BAC5.2 · Post by **BAC5.2** » Thu Jun 03, 2004 12:13 am

No problem, it's pretty cool how they work. I like the idea that it's a fully mechanically dependant rather than relying on a fluid to transfer power. Fluid shears, gears are a lot more durable.

free5ty1e · Post by **free5ty1e** » Thu Jun 03, 2004 12:24 am

Yeah, that sounds like it'd be pretty solid. Too bad its not an option.

Anyway - I have a new question. When the tires break loose in our cars, since we've got a center LSD and front/rear open diffs, what happens? All 4 tires don't actually break traction?

(of course, I mean upon straight-line acceleration... not braking or drifting)

THAWA · Post by **THAWA** » Thu Jun 03, 2004 12:28 am

with open diffs most if not all the power will be sent to one wheel on the front or rear axles. So you'd have two wheels spinning.

free5ty1e · Post by **free5ty1e** » Thu Jun 03, 2004 12:37 am

heh... thought so. Oh well. Still heads and tails above my old FWD wheel-hopping, diff-pin spitting Saturn.

Is the tranny OK with this?

Anyone know the specifics? Which two wheels - front-left & right-rear wheels... something like that? Which side of our front/rear diffs usually get the power, or is that even possible to determine?

Pure curiosity talkin here.

THAWA · Post by **THAWA** » Thu Jun 03, 2004 12:44 am

I THINK its random, dependns on which wheels get traction and which dont.

BAC5.2 · Post by **BAC5.2** » Thu Jun 03, 2004 1:14 am

The center diff tries to control speed differences between the ends. If the rear output shaft spins faster than the front, the fluid thickens and trys to keep the differences constant.

If all 4 break loose, as long as both outputs are going the same speed (in terms of fore and aft outputs), the center diff is doing it's job. 2 wheels will probably break loose (1 front, 1 rear).

Our cars, the non LSD models, are essentially 2wd.

Power won't unload front to rear, because of the LSCD (limited slip center diff), but it will unload side to side. Launch in the rain, and you'll see what happens when all 4 break loose.

Because the wheels unload side to side, this puts stress on the LSCD. When the inside front slips around a turn, power wants to go to that wheel (it's the path of least resistance). This increases the front output speed, and causes the LSCD to try and even out the load. Wheel slip of one wheel at one end is when you overcome the LSCD capabilities. Front and rear LSD's reduce the load on the LSCD by controlling wheel slip from side to side. The LSCD only then has to worry about keeping the axles as a whole spinning the same speed, and side-to-side slippage is controlled by the LSD's in the axles.

Follow?

With open diffs, if 2 break loose before 1 breaks loose, then everything is working perfectly. With LSD diffs, if all 4 break loose before 1 or 2 break loose, then everything is working perfectly.

BAC5.2 · Post by **BAC5.2** » Thu Jun 03, 2004 1:17 am

We have equal length shafts at all four corners. In the dry, each of the fronts have a fairly equal chance of breaking loose, and the same goes for the rear. If the LSCD does it's job, then there won't be any wheel spin in the dry until you are making ridiculous power.

I've never seen, in person, an AWD break traction in the dry (off the strip).

free5ty1e · Post by **free5ty1e** » Thu Jun 03, 2004 2:49 am

Thanks BAC... that makes sense.

Ahh, ridiculous power. That's the goal

"Hi Supernintendo Chaulmers... I'm Learnding!" -- Ralph Wiggum

BAC5.2 · Post by **BAC5.2** » Thu Jun 03, 2004 3:22 am

Just play in the rain. It's no great difficulty to get a stock SS "fun" in the rain. Plus, you can beat most cars in the rain. Ask Matt. He beat the 9 second ESX car in the rain.

evolutionmovement · Post by **evolutionmovement** » Thu Jun 03, 2004 6:15 am

I easily spin both fronts (fwd) in the wet if the wheel is straight and the road surface is even. No LSD of course, but the equal length shafts do make a difference. I can even power through turns with the outside front like on a Prelude if I balance the car right before going in.

Steve

BAC5.2 · Post by **BAC5.2** » Thu Jun 03, 2004 6:20 am

What about a Prelude?

evolutionmovement · Post by **evolutionmovement** » Thu Jun 03, 2004 6:41 am

The Prelude SH or whatever it was with the torque sensing diff.

Steve

rsstiboy · Post by **rsstiboy** » Thu Jun 03, 2004 1:41 pm

guarantee you only spin the front right if you are steering forward as the front diff is always a open diff on subaru's as it makes it easier to steer, the centre diff is a viscous unit as described earlier and the rear is a LSD unit also (australian models anyway) I have seen white smoke from my tyres on many occasions but only ever from the front right and both rears if i hang it far enough out around a corner. and for the record I regularly break traction at the strip in the dry.

BAC5.2 · Post by **BAC5.2** » Thu Jun 03, 2004 8:03 pm

evolutionmovement wrote:The Prelude SH or whatever it was with the torque sensing diff.

Steve

Ahh, any car with a Torsen LSD will do that.

I wish Quaife made LSD's for our cars

mTk · Post by **mTk** » Thu Jun 03, 2004 8:19 pm

BAC5.2 wrote:I wish Quaife made LSD's for our cars

They do..

MK

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5mt driveshaft question