Rear Differential Rebuild/With Pictures

[z122643]

If it is good it will slip but very slowly and with a lot of resistance. Remember it's a LSD not a locked differential.

[z122643]

So, I installed my rebuilt diff and now I can hear my radio... funny how that happens.

Despite how bad the old diff looks the LSD is in excellent shape. I intend to rebuild this one and either keep it for a rainy day or sell it.

[FredK]

Now that I've got someone's attention. Anyone know how to get the pinion out?

Either pound it out with a heavy dead blow hammer exactly in this state, or use a hydraulic press.

[Wanganstyle]

A diff with old pinion bearings and races and Old LSD internals is NOT rebuilt

BMW's kill the pinion bearings and races first; no amount of paint or clean up will "FIX" this.
to replace them with NEW is the proper procedure; a NEW crush washer is needed to set the drag load.

I could, but BMW used a VC back there for a reason - to some extent a clutch diff still needs one axle to have a load on it. a VC doesn't.

a Clutch type LSD unit locks because the basket of spider gears in the middle wants to expand when One wheel is significantly different than the other; One wheel can be airborne and unloaded; it will Lock if internally proper.

A viscous LSD uses HEAT from the wheel speed difference to lock up plates in fluid; its a REACTIONARY item that locks AFTER enough heat is put into it.

[TehRaydarlover]

A diff with old pinion bearings and races and Old LSD internals is NOT rebuilt

BMW's kill the pinion bearings and races first; no amount of paint or clean up will "FIX" this.
to replace them with NEW is the proper procedure; a NEW crush washer is needed to set the drag load.




a Clutch type LSD unit locks because the basket of spider gears in the middle wants to expand when One wheel is significantly different than the other; One wheel can be airborne and unloaded; it will Lock if internally proper.

A viscous LSD uses HEAT from the wheel speed difference to lock up plates in fluid; its a REACTIONARY item that locks AFTER enough heat is put into it.

A viscous lsd uses a shear thickening silicone fluid not heat, hence VISCOUS lsd. The fluid increases viscosity with shear rate. The diff will lock after it reaches a high enough shear rate. An increase in temperature would if anything make the fluid less viscous.

[Wanganstyle]

A viscous lsd uses a shear thickening silicone fluid not heat, hence VISCOUS lsd. The fluid increases viscosity with shear rate. The diff will lock after it reaches a high enough shear rate.

A viscous lsd uses a shear thickening silicone fluid not heat, hence VISCOUS lsd. The fluid increases viscosity with shear rate. The diff will lock after it reaches a high enough shear rate.

We are both saying the same thing.

Viscous silicone fluid still needs heat to work.

Heat comes from wheel speed differences


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[TehRaydarlover]

We are both saying the same thing.

Viscous silicone fluid still needs heat to work.

Heat comes from wheel speed differences


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No heat has nothing to do with it. Its an unwanted byproduct.

[Wanganstyle]

No heat has nothing to do with it. Its an unwanted byproduct.

Google search how a viscous lsd works: Suabru and many others use them. Bmw uses a GKN VISCO-LOK viscous on e46m3 and e60 m5; im quite familiar with it.

If it was not heat expanding the silicon viscous fluid then how else would it lock up? MAGIC???

The viscous unit is a sealed capsule with fluid and discs inside. The silicon fluid gets hot and expands: locking happens then

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[nando]

actually I agree with him - you have it wrong. viscosity increases because of shear, not because of heat. heat is just a byproduct.

[Wanganstyle]

actually I agree with him - you have it wrong. viscosity increases because of shear, not because of heat. heat is just a byproduct.

Subaru factory explains it as heat expansion causing viscosity increase.



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[TehRaydarlover]

Google search how a viscous lsd works: Suabru and many others use them. Bmw uses a GKN VISCO-LOK viscous on e46m3 and e60 m5; im quite familiar with it.

If it was not heat expanding the silicon viscous fluid then how else would it lock up? MAGIC???

The viscous unit is a sealed capsule with fluid and discs inside. The silicon fluid gets hot and expands: locking happens then

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lol its a material property. Simple example: have you ever played with cornstarch and water??? It gets hard when you try to stir it. It does not get hot... a lsd is fundamentally the same thing

actually I agree with him - you have it wrong. viscosity increases because of shear, not because of heat. heat is just a byproduct.

^this

[Wanganstyle]

lol its a material property. Simple example: have you ever played with cornstarch and water??? It gets hard when you try to stir it. It does not get hot... a lsd is fundamentally the same thing



^this

Chicken egg equation

Realistically the plates inside vlsd will expand with heat.

This is a math bee beteeen tmi school kids

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[TehRaydarlover]

Chicken egg equation

Realistically the plates inside vlsd will expand with heat.

This is a math bee beteeen tmi school kids

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How hot do you think it gets??? The plates will never expand enough to make the diff lock. If that was the case you would have to wait a while for the plates to cool down for the diff to open back up.

lol, yep. I am a senior ME student, I've done experiments with Newtonian and non-Newtonian fluids, and plotted the shear rate vs viscosity. The fluid in the vlsd is a silicone based dilatant fluid. Do some searches about vlsd on pages other than Wikipedia, you'll see what I'm trying to say.

[Wanganstyle]

A tiny bit. Not some extrene

Research and ask your professors

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[TehRaydarlover]

I've done the research and the experiments to prove it. Evidently you haven't.