Please explain cast iron Differentials ?

[Jimbo76]

Lurking here for awhile I have questions about differentials. It seems a locking differential (adventure package) is available for the H3 in cast iron. My question is what are they normally made of and what part of the axle assembly is "cast iron". Is it internal where the ring gear is or is it the whole axle from wheel to wheel that is the desirable part to get ? In the old days we called it a pumpkin. My end desire is to lock front and rear and what is needed to do this. Thanks in advance.

[cdmintmi]

i think the difference is only the t-case housing is cast iron. the others got an alluminum housing. not positive, but pretty sure

[3Hummer]

its mainly in part to support the extra weight and the proposed more abuse that an Alpha would get.

[trailerpup]

It is the front differential which is cast iron. That is the center section of the front axle. All of the transfer cases are aluminum. The switch to cast iron for the front differential was made due to the original aluminum housing flexing under "extreme" situation which resulting in the front differential breaking gears in the ring and pinion. If you do not abuse your rig you should have no problem with the aluminum differential housing. The Alpha is rated at higher torque and horsepower, just be sure they upgraded the material. Swapping out the aluminum housing for a cast iron unit is an "upgrade" that some I5 owners have done.