Reply to "ZF crack question"

The ZF has three main castings, plus the bellhousing. The aluminum ones are structural members so magic glues will not remedy the flexing that works the crack and will only grow worse. The first casting is directly bolted to the bellhousing and holds the differential. There is a rectangular access cover bolted to the bottom of this casting. The second part, only about 8" long, holds the transmission gears and the rearmost part is a shaft cover of cast iron.

If I interpret your description correctly, the leak is in the transmission casting. Cracking can happen there if someone unknowingly unbolts the speedometer angle-drive on the right side, behind the halfshafts. Done wrong, this frees up a 4" extension shaft to FALL INSIDE! There's not much extra room in there so driving the car with the shaft loose inside can and has driven that shaft into the case, cracking it & wrecking the little $250 shaft. I've welded up a couple of cases from this. I've also seen other loose metal parts drift around inside and get caught in the gear mesh, with similar results. The scary part is, you don't know if the chunk is still in there.... Spraying degreaser on the case, wipe clean and watch for appearance of a drop of lube should tell you whats happened. Maybe you'll be lucky and only have a loose or stripped metric allen bolt holding the trans-case to the diff-case.

If it IS cracked and I were you & didn't know ZFs intimately, I would bite the bullet and ship the whole ZF to RBT Transmissions in Los Angeles for tear-down and repair. Figure $1500 minimum charge if nothing else is wrong inside. FWIW, that is an $8000+ transaxle (once fixed) you have there! Aluminum cases are easy to weld (with heli-arc) but the innards must be out and the aluminum degreased to get weld to stick.

The ZF and bellhousing unbolts & slides back 6" to clear the clutch, then hoists out without otherwise disturbing the engine. It weighs 160 lbs in this condition- get a friend or two to help, and a hoist. And be careful not to hurt anyone, or bash the car. Good luck.