Importance of LSD?

whatnot said:

....I think it will be a bit better in the snow, but I haven't driven in the snow yet. .....

Click to expand...

With good tires it will but only to an extent.

2 examples I can give you of why:

-Sometime when I park near the sidewalk and there's about 3-4 inches of packed snow, when leaving if I give just enough throttle to get the car moving the back, wheels will spin a bit, lock the diff, and then dig themselves in the snow that's on the ground...

Other side to this is the fact that if you dig 1 wheel in, the diff won't transfer any power to the stuck wheel if the other one spins freely, just like an open diff. The Torsen unit needs to see some Tq on both wheels to effectively transfer Tq and "lock".

Look in my Sig Picture. It seems there's a lot of snow, but there's only about 2-3" max. When parked like that the rear end likes to swerve towards the sidewalk since the streets are a bit crested/crowned.

-Other times the LSD is somewhat not that beneficial in winter is when driving on roads that have, let's say 70-80%, adherence, is that sometimes when you accelerate you'll hit peak boost/tq, the back end gets a bit loose and the diff "locks" and you get a bit of wheel spin/fish tail thing going.

Not cool when the car gets "tail-happy" @ 40-50 mph.:hsugh:

And since you're car's not stock anymore, you know...:ugh:

Buuuuut, the LSD in the GC on dry pavement -> Om nom nom nom, it likes to eat asphalt

...Where the heck (in that LSD vs. non-LSD thread... oops) are people getting the idea that an open differential is one-wheel-drive and that only one of your wheels is a drive wheel?

An open-differential is still two-wheel drive. It will usually transmit torque equally to both tires (proportional to their differential rates of spin, so the wheel spinning faster gets more torque). The problem is that if one wheel starts slipping, that wheel eats almost all of the torque and the non-slipping wheel (where you want the traction) gets none, causing a characteristic one-wheel-spin. It's still entirely possible to do a two-wheel burnout with a conventional open differential, but you have to get both wheels slipping simultaneously so they both equal out on torque. This is easier said than done, but if you drop the clutch at 6000 RPM in any classic hot-rod RWD car before LSDs became commonplace, the torque thrown at both wheels before either slips will be more than enough to kick them both into a spin.

A limited slip differential locks the differential depending on torque input or engine braking, so that the free-spinning wheel is matched to the speed of the slower-spinning/non-spinning wheel and its torque is diverted back to where it can apply friction to the road. When cruising at a fixed speed, no effective torque is being produced and the differential unlocks to let the wheels turn at different rates as needed.

The drawback to an LSD is increased cost and weight. The benefits are higher traction under acceleration (all types) and/or deceleration (1.5- or 2-way differentials). Benefits are higher for FWD vehicles (to counteract understeer), but will still benefit RWD vehicles. From what I understand, and based on my experience with an open-diff FWD and a limited-slip RWD it's much better.

You also have to manage your throttle better, though. It's easier to spin both wheels loose with an LSD, because if you accelerate hard enough to slip one wheel, that torque transferred over to the other wheel will probably slip it too. The ideal is to keep your tires in static friction, and the LSD will benefit you greatly when you drive in that way. And if you want to kick your wheels loose for a drift or touge, an LSD helps you do that too.