Slipping LSD

[RonD]

No fighting

Actually yes, it would drive off the jack, unless the clutch packs were burnt out

Google: How Clutch Type Limited Slip Differentials Work

Good video, only need to watch the video about 1/2 way thru

Earlier in the video he also compares how the gear type limited slip work vs clutch pack type
Also the viscous/gel type LSD, only heard of them once but never new how they worked

Ford and GM used a similar setup
Outer case is bolted to ring gear, and the case is connected to every other clutch plate, so these plates spin at ring gear RPMs
Axles are connected to the in between clutch plates
The clutch plates are press together by the pre-load spring so are locked at that point so both axles spin at ring gear RPMs

Takes about 40ft/lb of torque to spin one axle while holding the other, with friction modifier in the oil, which does show that they are locked, but have "limited" slip

 

[4x4junkie]

Have to go with @00t444e and @gw33gp on this.

A "locked" differential is exactly just that; it has some form of a mechanical engagement mechanism (teeth, splines, clutch gear, etc.) that prevents either axle shaft from ever turning slower than the ring gear. A sticking limited slip differential certainly is not that.

For the above reason, the Auburn Gear ECTED "locker" also is not a true locker, since it "locks" via a ball-ramp mechanism that merely preloads a limited-slip clutch pack tighter. Under some (actually, many) conditions they can still slip even when "locked".

 

[RonD]

Exactly, a clutch pack is "locked" as it sits, its "normal" state, but allows slipping as required by conditions, unlike a welded axle setup

A "locker" is an OPEN differential until it's physically locked, electric or mechanical
As said in the video the gear type LSD can suddenly switch to OPEN with sudden loss of traction on one wheel, and spinning wheel get all the power

I guess we will have to agree to disagree on the physics of these different setups

 

[BroncLander]

Is the Dana 28 worth putting a lunchbox locker in? Or would it be a pain in the arse and just break stuff?

 

[lowspeedpursuit]

I'm actually curious about this: do they still make D28 lockers anyway? A quick search shows a very rare factory LSD and a discontinued Powertrax lock-right.

 

[00t444e]

Takes about 40ft/lb of torque to spin one axle while holding the other, with friction modifier in the oil, which does show that they are locked, but have "limited" slip

Do you realize that makes no sense at all? Don't worry I will fix it for you.

Takes about 40ft/lb of torque to spin one axle while holding the other, with friction modifier in the oil, which does show that they are not locked, but have "limited" slip

You're welcome.

 

[RonD]

I think you have reversed the laws of physics in your correction

Axles are locked together until enough force/torque is applied to one axle/wheel allowing it to "slip", like when going around a corner, the other axle stays locked
And once the torque difference is removed, both wheels tuning at the same RPM, both axles are again locked together

 

[00t444e]

I think you have reversed the laws of physics in your correction

Axles are locked together until enough force/torque is applied to one axle/wheel allowing it to "slip", like when going around a corner, the other axle stays locked
And once the torque difference is removed, both wheels tuning at the same RPM, both axles are again locked together

No, locked axles are locked mechanically and never allow slip between both wheels. By your logic an open differential would also be "locked" when you are going straight.

 

[gw33gp]

Ron, I think your definition of locked, is the problem. When something is lockable it is either locked or unlocked. It can't slip to be unlocked and it can't be partially locked. That is what an automatic locker like a Detroit locker does. That is not an LSD.

The LSD clutches can be engaged and turn together until the force between the two is enough to make them slip. They are never locked together. You would have to have something like dowels or teeth going from one to another to have it locked. Then they would have to be pulled apart to disengage the dowels to unlock them. That would not be slipping or an LSD.

 

[RonD]

The conversation is about Limited Slip, not physically locked axles that can never unLock

My point was that clutch pack limited slip are LOCKED as their natural state, but are allowed to slip when needed

Gear driven limited slip are OPEN as their natural state but can LOCK as needed

And then there are Locking differentials that are control electrically or mechanically from an outside source, OPEN until LOCKED, but no slipping state, so straight line driving or off-road, until turned off

And then there are welded together axles, always LOCKED, no slipping ever

 

[pjtoledo]

why is it called limited slip when it's actually "when it hits the limit, it slips"

I would like to propose that "limited power" is a more applicable term.

 

[sgtsandman]

Perhaps coupled would be a better term than locked for an LSD.

For all intents and purposes, a locked differential is where the axles are “fused” together and won’t disconnect until the locker is shut off or disengaged.

An LSD does engaged both axles but only up until a certain point where the clutches can no longer keep the axles turning at the same RPM

A locker doesn’t do that. Something else has to let go to relieve the binding and stresses. Either tire grip or an axle shaft. Usually, it’s the tire.

 

[RonD]

"Limited Power" wouldn't work

If the power from drive shaft was say 100% and each axle was 50% in this example(actually both LOCKED axles would also be 100%, lol)

With limited slip if one axle was using 60%(wheel lost traction) then the function of the limited slip would be to transfer that 60%(-10% from slipping wheel and +10% to non-slipping wheel) to the other axle leaving the slipping wheel only 40% so it would stop spinning and hopefully regain traction

So at any given time at least one axle will have the full power from the drive shaft, so there is never "limited power" except maybe in the spinning/slipping wheel but that's not caused by the LSD but by the road surface and loss of traction

 

[gw33gp]

Perhaps coupled would be a better term than locked for an LSD.

For all intents and purposes, a locked differential is where the axles are “fused” together and won’t disconnect until the locker is shut off or disengaged.

An LSD does engaged both axles but only up until a certain point where the clutches can no longer keep the axles turning at the same RPM

A locker doesn’t do that. Something else has to let go to relieve the binding and stresses. Either tire grip or an axle shaft. Usually, it’s the tire.

I like the term coupled with respect to an LSD. That is what is going on.

I don't agree with gear a driven LSD is open naturally. They also don't lock. The torque bias can increase under acceleration and can kind of act like a locker, but they are not locked.

I have driven about every kind of differential there is. I actually ran an entire race with a broken drive axle. Fortunately, I had my Detroit locker in the race car. The axle broke on the way to pregrid and I did not know it. When we got the green, I floored it and just smoke one tire. It didn't take me long to figure out I had a broken drive axle. I spent half of the race figuring out how to drive the one-wheel drive car. Going left, the left wheel would spin if I put any power down. Going right, I could use power as I normally did. At Laguna Seca most turns are left. We got a full course yellow shortly after halfway through the race, and I was able to catch up to my main competition. I followed him to find where I could use my car's advantage to pass. On the last lap before the long hill, I used my momentum to pass after a left turn and out outpowered up the hill. I got far enough ahead to finish in first place.

The reason for this long story is, I could never have been able to complete this race if I had an LSD in the car. They don't lock and I would have had no drive.

 

[bobbywalter]

Yeah.