How important is an LSD on this car?

[Dimman]

Originally Posted by ToyotaObsession

That's what a VLSD is. It's a very thick fluid that allows a little bit of slippage, but once starts to turn too much the fluid starts to act like glue to transfer more torque to it.

Very inefficient as it's easy to overcome the fluid.

Not exactly, it starts off thin, and gets thicker as it heats up. The thicker it gets the more difficult it is to flow and the more engagement happens.

I've never driven one, but I've heard they don't engage progressively. Kind of do nothing, then 'turn on'. Like it's a squared relation instead of linear or something.

[OldSkoolToys]

Originally Posted by ToyotaObsession

That's what a VLSD is. It's a very thick fluid that allows a little bit of slippage, but once starts to turn too much the fluid starts to act like glue to transfer more torque to it.

Very inefficient as it's easy to overcome the fluid.

Ok, obvious you didn't click my link, nor read the information. And obviously you are really really unaware of what LSD's Toyota uses, because it is NOT a viscous LSD. Infact I'm pretty sure Toyota has never used viscous in any of their cars.

I know for a -fact- I'm right on the separate chamber bit. There is a completely different chamber inside the differential unit, full of silicone fluid, that acts as the "LSD" part of a viscous diff. The drain/refill plugs are for the normal gear oil ONLY. You can't drain, nor change, the silicone fluid. Viscous differentials are not like mechanical differentials. In a viscous LSD you don't have to put any LSD additive in the regular gear oil, as the oil in that area is effectively lubricating a normal differential. LSD additives are for adding friction across the clutches.

Originally Posted by Dimman

Not exactly, it starts off thin, and gets thicker as it heats up. The thicker it gets the more difficult it is to flow and the more engagement happens.

I've never driven one, but I've heard they don't engage progressively. Kind of do nothing, then 'turn on'. Like it's a squared relation instead of linear or something.

Yeah, basically the LSD doesn't work until slippage has already occured. It has to be 'activated' I guess in this sense, unlike a mechanical LSD, like a clutch type, that basically can lock once acceleration / braking is applied.

[Ryephile]

OldSkool is right; there are applications where the viscous fluid is in a separate chamber. I vaguely remembered the early 1.6L NA Miata's having this, so I looked it up and found this quote in Wikipedia:

Originally Posted by Wikipedia

Viscous LSDs are less efficient than mechanical types, that is, they "lose" some power. In particular, any sustained load which overheats the silicone results in sudden permanent loss of the differential effect.[4] They do have the virtue of failing gracefully, reverting to semi-open differential behaviour. Typically a visco-differential that has covered 60,000 miles (97,000 km) or more will be functioning largely as an open differential;[citation needed] this is a known weakness of the original Mazda MX-5 (a.k.a. Miata) sports car. The silicone oil is factory sealed in a separate chamber from the gear oil surrounding the rest of the differential. This is not serviceable and when the differential's behaviour deteriorates, the VLSD centre is replaced.

Source

[OldSkoolToys]

Originally Posted by Ryephile

OldSkool is right; there are applications where the viscous fluid is in a separate chamber. I vaguely remembered the early 1.6L NA Miata's having this, so I looked it up and found this quote in Wikipedia:



Source

I'd challenge then for someone to provide an example of a true viscous LSD where the silicone fluid is combined with the regular gear oil, and not separated. Because all I know about are the Viscous LSD's where the chamber is separated. I mean, thats the entire design of the differential itself!

[ToyotaObsession]

Originally Posted by OldSkoolToys

Ok, obvious you didn't click my link, nor read the information. And obviously you are really really unaware of what LSD's Toyota uses, because it is NOT a viscous LSD. Infact I'm pretty sure Toyota has never used viscous in any of their cars.

I know for a -fact- I'm right on the separate chamber bit. There is a completely different chamber inside the differential unit, full of silicone fluid, that acts as the "LSD" part of a viscous diff. The drain/refill plugs are for the normal gear oil ONLY. You can't drain, nor change, the silicone fluid. Viscous differentials are not like mechanical differentials. In a viscous LSD you don't have to put any LSD additive in the regular gear oil, as the oil in that area is effectively lubricating a normal differential. LSD additives are for adding friction across the clutches.



Yeah, basically the LSD doesn't work until slippage has already occured. It has to be 'activated' I guess in this sense, unlike a mechanical LSD, like a clutch type, that basically can lock once acceleration / braking is applied.

If you read what I wrote, I never claimed that Toyota had used a VLSD in anything.

Calm down dude lol. I just said I hadn't heard of it before just that they suck, and they do. A little bit a googling and yes you're right. It's a separate chamber. Horrible design, very little benefit.

[Allch Chcar]

Originally Posted by OldSkoolToys

I'd challenge then for someone to provide an example of a true viscous LSD where the silicone fluid is combined with the regular gear oil, and not separated. Because all I know about are the Viscous LSD's where the chamber is separated. I mean, thats the entire design of the differential itself!

Mustang LSD?

Edit: Found it.
How to change a Mustang differential fluid.

Edit: Step #12

[Ryephile]

Sorry Allch, the Mustang LSD's are clutch-pack. They go by the brand name "Traction-Lok". The how-to you found only proves it; they're using normal gear lube with clutch-pack friction modifier additive. See the additive description here.

[Allch Chcar]

Originally Posted by Ryephile

Sorry Allch, the Mustang LSD's are clutch-pack. They go by the brand name "Traction-Lok". The how-to you found only proves it; they're using normal gear lube with clutch-pack friction modifier additive. See the additive description here.

Whoops, my bad.

[Ryephile]

It's ok. I used to have Mustang and I know them quite well. IIRC, no American brand recently has implemented a viscous LSD mainly because they're weird and more complicated than a good ole' cheap clutch-pack LSD.