RX-Ben

Anyone know if there are any grease packed bearings in an FD Torsen LSD?

Are the carrier bearings grease packed?

Thanks
Ben

KevinK2

all internals are lubed by the fill gear oil. Only rolling element bearings are the carrier bearings. friction at gear mesh and thrust surfaces define the degree of lock-up .... extra modifiers ( slippery stuff from GM or redline) will reduce lock-up.

RX-Ben

Thanks very much for the reply- I'm getting the LSD cryo treated and was just making sure there wouldn't be any problems due to grease packed bearings.

Thanks
Ben

Cheers!

save your money on the cryo treating BS

RX-Ben

Care to explain your position?

Cheers!

Cryo treating aka freezing metal to temperatures at which nitrogen or helium are liquids do not change the grain structure of the metal. The grain structure is determined by the rate at which the metal cool when brought up to a tempering temperature. For iron alloys you are looking for martinsite grain structure, which is accomplished by rapidly cooling the metal such that it passes through certain regions on the phase diagram. For aluminum it is not largely dependant on the grain structure, it is more dependant on the alloying content and the heat treatment of the aluminum to relieve internal stresses by tempering at temperatures above zero degrees C.

If you look at any phase diagram in any metalurgical text book you will see the phase diagram stops at around room temperature, since nothing happens beyond that point.

mad_7tist

/\ ok. well nascar is spending a ton of money on it now that they have limited engines for qualfying and racing. some places may not do it correctly but race teams do report better life/wear etc...

RX-Ben

Here is more info on cryo treatment "bs"-

http://lennon.pub.csufresno.edu/~rlk16/cryo.html

http://www.memagazine.org/backissues...ig/thebig.html

Slacker7

iTrader: (2)

Cryotreatment is done to acchieve the same effect as shot peening which is to create compressive residual streeses on a part to improve fatigue performance and not to change it's grain structure.

RX-Ben

from what I've read- shot peening only affects the surface of the piece (and just under the surface) as opposed to treating the whole piece like cryo does.

KevinK2

not true.

shot peening is as stated, and mainly to avoid cracking due to fatigue. I've spec'd it many times.

Cryo does change the grain structure, and is mainly for improved wear in heat treated med/high carbon steels (gears, tooling dies). Also works on brake rotors. I have not seen any data to support any fatigue life improvements.

Nitriding carbon steel creats hard, compressive layer in steel that resists wear and fatigue.

A torsen lsd has lots of thrust loads on the planet gears, and may benefit from cryo treatment. It may also change the degree of lock-up.